Substituted xanthine derivatives

ABSTRACT

This invention relates to novel deuterated compounds that are substituted xanthine derivatives and pharmaceutically acceptable salts thereof. In particular, this invention relates to novel substituted xanthine derivatives that are deuterated derivatives of a pentoxifylline metabolite. This invention also provides compositions comprising one or more compounds of this invention and a carrier and the use of the disclosed deuterated compounds and compositions in methods of treating diseases and conditions for which pentoxifylline and related compounds are beneficial. The compounds of the invention are represented by the following structural formula: 
     
       
         
         
             
             
         
       
     
     wherein the values of R 1 , R 2 , R 3 , R 4 , R 5 , Y 1  and Y 2  are described herein.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/067,736, filed on Feb. 29, 2008, U.S. Provisional Application No.61/134,568, filed on Jul. 11, 2008 and U.S. Provisional Application No.61/198,715, filed on Nov. 7, 2008. The entire teachings of the aboveapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Pentoxifylline, 1-(5-oxohexyl)-3,7-dimethylxanthine, is sold under thename Trental® in the U.S. and Canada. It is currently approved for thetreatment of patients with intermittent claudication on the basis ofchronic occlusive arterial disease of the limbs. It is also in clinicaltrials for glomerulonephritis, nephrotic syndrome, nonalcoholicsteatohepatitis, Leishmaniasis, cirrhosis, liver failure, Duchenne'smuscular dystrophy, HIV infection, late radiation induced injuries,radiation induced lymphedema, alcoholic hepatitis, radiation fibrosis,necrotizing enterocolitis in premature neonates, chronic kidney disease,pulmonary sarcoidosis, recurrent aphthous stomatitis, chronic breastpain in breast cancer patients, brain and central nervous system tumors,and malnutrition-inflammation-cachexia syndrome. Pentoxifylline has alsorecently garnered attention as a potential treatment for diabetes anddisorders associated with diabetes. See Ferrari, E et al.,Pharmatherapeutica, 1987, 5(1): 26-39; Raptis, S et al., Acta DiabetolLat, 1987, 24(3):181-92; and Rahbar, R et al., Clin Chim Acta, 2000,301(1-2): 65-77.

Pentoxifylline is known to have activity as an inhibitor ofphosphodiesterase (PDE; see Meskini, N et al,. Biochem. Pharm. 1994,47(5): 781-788) as well as activity against other biological targets,but its exact mode of action leading to clinical effects is unknown.Pentoxifylline has been shown to improve blood flow properties throughhemorheologic effects which lower blood viscosity and improveerythrocyte flexibility. Pentoxifylline also increases leukocytedeformability and inhibits neutrophil adhesion and activation. (See FDAlabel for pentoxifylline at http://www.fda.gov/cder/foi/nda/99/74-962Pentoxifylline_prntlbl.pdf). In addition to improving hemorheologicproperties, pentoxifylline is also believed to have anti-inflammatoryand anti-fibrotic properties.

The clinical pharmacology of pentoxifylline has been attributed to theparent drug as well as its metabolites, though the sequence of eventsleading to clinical improvement is still to be defined. Pentoxifyllineundergoes rapid first pass metabolism. Peak plasma levels ofpentoxifylline and its metabolites are reached within one hour.Structures of pentoxifylline and its various reported metabolites areshown below.

The major metabolites generated are M-1 and M-5. Plasma levels of thesemetabolites are five and eight times greater, respectively, than theparent drug. (See FDA label for pentoxifylline athttp://www.fda.gov/cder/foi/nda/99/74-962_Pentoxifylline_prntlbl.pdf).The M-1 metabolite has a chiral center and both the (R)- and(S)-enantiomers are formed. During the metabolism of pentoxifylline, aninterconversion takes place between the M-1 enantiomers andpentoxifylline. The (S)-enantiomer is the predominant M-1 species (ratioof S:R is reported to be approximately 90:10 or greater) andinterconverts more rapidly than the (R)-enantiomer. The minor (R)-M1metabolite (known as lisofylline) is reported to have novelanti-inflammatory properties.

While active M1 metabolite appears to play a central role in theclinical activity of pentoxifylline, other metabolites may contribute todrug toxicity. Notably, the risk of toxic reactions to pentoxifyllinemay be greater in patients suffering from renal impairment(http://products.sanofi-aventis.us/trental/trental.pdf). According toproduct labels, patients with renal impairment who take the drug requirethe monitoring of renal function. Moreover, at least one product labelwarns that pentoxifylline should not be administered to patients withsevere renal or hepatic impairment. See Trental® Product Monograph,Canada, Dec. 16, 2008. In patients with renal impairment, it wasreported that the plasma levels of pentoxifylline and M-1 exhibited adownward trend, while the levels of the M-4 and especially M-5metabolite increased greatly depending on the degree of impairment. SeePaap, Ann. Pharmacother., 1996, 30: 724. Taken together theseobservations suggest that accumulation of the M5 metabolite may beresponsible for the reduced tolerability in patients with renaldysfunction.

Other compounds that are structurally related to pentoxifylline havebeen reported to be biologically active. Examples of such compoundsinclude albifylline, torbafylline, A-802715, and propentofylline shownbelow.

Despite the beneficial activities of pentoxifylline, there is acontinuing need for new compounds to treat the aforementioned diseasesand conditions in a greater patient population while mitigating the riskof toxic reactions and other adverse effects.

SUMMARY OF THE INVENTION

This invention relates to novel compounds that are substituted xanthinederivatives and pharmaceutically acceptable salts thereof. For example,this invention relates to novel substituted xanthine derivatives thatare structurally related to pentoxifylline. This invention also providescompositions comprising one or more compounds of this invention and acarrier and the use of the disclosed compounds and compositions inmethods of treating diseases and conditions for which pentoxifylline andrelated compounds are beneficial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B depict the serum levels of a compound of this invention,pentoxifylline and certain of their respective metabolites in fourindividual dogs following oral administration of a combination ofpentoxifylline and that compound of this invention.

FIG. 2 depicts the time course of the production of the specificmetabolites measured in FIG. 3 following incubation of various compoundsof this invention, pentoxifylline, (S)-M1 and (R)-M1 with rat wholeblood.

FIG. 3 depicts the relative amount of specific metabolites producedfollowing incubation of various compounds of this invention,pentoxifylline, (S)-M1 and (R)-M1 with rat whole blood.

FIG. 4 depicts the time course of the production of the specificmetabolites measured in FIG. 5 following incubation of various compoundsof this invention, pentoxifylline, (S)-M1 and (R)-M1 with human livermicrosomes.

FIG. 5 depicts the relative amount of specific metabolites producedfollowing incubation of various compounds of this invention,pentoxifylline, (S)-M1 and (R)-M1 with human liver microsomes

DETAILED DESCRIPTION OF THE INVENTION

The terms “ameliorate” and “treat” are used interchangeably and includeboth therapeutic and prophylactic treatment. Both terms mean decrease,suppress, attenuate, diminish, arrest, or stabilize the development orprogression of a disease (e.g., a disease or disorder delineatedherein), lessen the severity of the disease or improve the symptomsassociated with the disease.

“Disease” means any condition or disorder that damages or interfereswith the normal function of a cell, tissue, or organ.

It will be recognized that some variation of natural isotopic abundanceoccurs in a synthesized compound depending upon the origin of chemicalmaterials used in the synthesis. Thus, a preparation of pentoxifyllinewill inherently contain small amounts of deuterated isotopologues. Theconcentration of naturally abundant stable hydrogen and carbon isotopes,notwithstanding this variation, is small and immaterial as compared tothe degree of stable isotopic substitution of compounds of thisinvention. See, for instance, Wada E et al., Seikagaku, 1994, 66: 15;Gannes L Z et al., Comp Biochem Physiol Mol Integr Physiol, 1998, 119:725. In a compound of this invention, when a particular position isdesignated as having deuterium, it is understood that the abundance ofdeuterium at that position is substantially greater than the naturalabundance of deuterium, which is 0.015%. A position designated as havingdeuterium typically has a minimum isotopic enrichment factor of at least3340 (50.1% deuterium incorporation) at each atom designated asdeuterium in said compound.

The term “isotopic enrichment factor” as used herein means the ratiobetween the isotopic abundance and the natural abundance of a specifiedisotope.

In other embodiments, a compound of this invention has an isotopicenrichment factor for each designated deuterium atom of at least 3500(52.5% deuterium incorporation at each designated deuterium atom), atleast 4000 (60% deuterium incorporation), at least 4500 (67.5% deuteriumincorporation), at least 5000 (75% deuterium), at least 5500 (82.5%deuterium incorporation), at least 6000 (90% deuterium incorporation),at least 6333.3 (95% deuterium incorporation), at least 6466.7 (97%deuterium incorporation), at least 6600 (99% deuterium incorporation),or at least 6633.3 (99.5% deuterium incorporation).

In the compounds of this invention any atom not specifically designatedas a particular isotope is meant to represent any stable isotope of thatatom. Unless otherwise stated, when a position is designatedspecifically as “H” or “hydrogen”, the position is understood to havehydrogen at its natural abundance isotopic composition. Also unlessotherwise stated, when a position is designated specifically as “D” or“deuterium”, the position is understood to have deuterium at anabundance that is at least 3340 times greater than the natural abundanceof deuterium, which is 0.015% (i.e., at least 50.1% incorporation ofdeuterium).

The term “isotopologue” refers to a species that differs from a specificcompound of this invention only in the isotopic composition thereof.

The term “compound,” when referring to a compound of this invention,refers to a collection of molecules having an identical chemicalstructure, except that there may be isotopic variation among theconstituent atoms of the molecules. Thus, it will be clear to those ofskill in the art that a compound represented by a particular chemicalstructure containing indicated deuterium atoms, will also contain lesseramounts of isotopologues having hydrogen atoms at one or more of thedesignated deuterium positions in that structure. The relative amount ofsuch isotopologues in a compound of this invention will depend upon anumber of factors including the isotopic purity of deuterated reagentsused to make the compound and the efficiency of incorporation ofdeuterium in the various synthesis steps used to prepare the compound.However, as set forth above, the relative amount of such isotopologuesin toto will be less than 49.9% of the compound.

The invention also provides salts of the compounds of the invention. Asalt of a compound of this invention is formed between an acid and abasic group of the compound, such as an amino functional group, or abase and an acidic group of the compound, such as a carboxyl functionalgroup. According to another embodiment, the compound is apharmaceutically acceptable acid addition salt.

The term “pharmaceutically acceptable,” as used herein, refers to acomponent that is, within the scope of sound medical judgment, suitablefor use in contact with the tissues of humans and other mammals withoutundue toxicity, irritation, allergic response and the like, and arecommensurate with a reasonable benefit/risk ratio. A “pharmaceuticallyacceptable salt” means any non-toxic salt that, upon administration to arecipient, is capable of providing, either directly or indirectly, acompound of this invention. A “pharmaceutically acceptable counterion”is an ionic portion of a salt that is not toxic when released from thesalt upon administration to a recipient.

Acids commonly employed to form pharmaceutically acceptable saltsinclude inorganic acids such as hydrogen sulfide, hydrochloric acid,hydrobromic acid, hydroiodic acid, sulfuric acid and phosphoric acid, aswell as organic acids such as para-toluenesulfonic acid, salicylic acid,tartaric acid, bitartaric acid, ascorbic acid, maleic acid, besylicacid, fumaric acid, gluconic acid, glucuronic acid, formic acid,glutamic acid, methanesulfonic acid, ethanesulfonic acid,benzenesulfonic acid, lactic acid, oxalic acid, para-bromophenylsulfonicacid, carbonic acid, succinic acid, citric acid, benzoic acid and aceticacid, as well as related inorganic and organic acids. Suchpharmaceutically acceptable salts thus include sulfate, pyrosulfate,bisulfate, sulfite, bisulfite, phosphate, monohydrogenphosphate,dihydrogenphosphate, metaphosphate, pyrophosphate, chloride, bromide,iodide, acetate, propionate, decanoate, caprylate, acrylate, formate,isobutyrate, caprate, heptanoate, propiolate, oxalate, malonate,succinate, suberate, sebacate, fumarate, maleate, butyne-1,4-dioate,hexyne-1,6-dioate, benzoate, chlorobenzoate, methylbenzoate,dinitrobenzoate, hydroxybenzoate, methoxybenzoate, phthalate,terephthalate, sulfonate, xylene sulfonate, phenylacetate,phenylpropionate, phenylbutyrate, citrate, lactate, β-hydroxybutyrate,glycolate, maleate, tartrate, methanesulfonate, propanesulfonate,naphthalene-1-sulfonate, naphthalene-2-sulfonate, mandelate and othersalts. In one embodiment, pharmaceutically acceptable acid additionsalts include those formed with mineral acids such as hydrochloric acidand hydrobromic acid, and especially those formed with organic acidssuch as maleic acid.

The invention also includes solvates and hydrates of the compound of theinvention. As used herein, the term “hydrate” means a compound whichfurther includes a stoichiometric or non-stoichiometric amount of waterbound by non-covalent intermolecular forces. As used herein, the term“solvate” means a compound which further includes a stoichiometric ornon-stoichiometric amount of solvent such as water, acetone, ethanol,methanol, dichloromethane, 2-propanol, or the like, bound bynon-covalent intermolecular forces.

It is understood that the carbon atom that bears substituents Y¹ and Y²in Formulae A, A1, I and B can be chiral in some instances (when Y¹, Y²and R³ are different from one another) and in other instances it can beachiral (when at least two of Y¹, Y² and R³ are the same). This carbonatom (i.e., the carbon atom bearing Y¹ and Y²) is indicated by an “*” inFormulae A, A1, I and B. As such, chiral compounds of this invention canexist as either individual enantiomers, or as racemic or scalemicmixtures of enantiomers. Accordingly, a compound of the presentinvention will include racemic and scalemic enantiomeric mixtures, aswell as individual respective stereoisomers that are substantially freefrom another possible stereoisomer. The term “substantially free ofother stereoisomers” as used herein means less than 25% of otherstereoisomers, preferably less than 10% of other stereoisomers, morepreferably less than 5% of other stereoisomers and most preferably lessthan 2% of other stereoisomers, or less than “X”% of other stereoisomers(wherein X is a number between 0 and 100, inclusive) are present.Methods of obtaining or synthesizing an individual enantiomer for agiven compound are well known in the art and may be applied aspracticable to final compounds or to starting material or intermediates.

Unless otherwise indicated, when a disclosed compound is named ordepicted by a structure without specifying the stereochemistry and hasone or more chiral centers, it is understood to represent all possiblestereoisomers of the compound.

The term “stable compounds,” as used herein, refers to compounds whichpossess stability sufficient to allow for their manufacture and whichmaintain the integrity of the compound for a sufficient period of timeto be useful for the purposes detailed herein (e.g., formulation intotherapeutic products, intermediates for use in production of therapeuticcompounds, isolatable or storable intermediate compounds, treating adisease or condition responsive to therapeutic agents).

“D” refers to deuterium. “Stereoisomer” refers to both enantiomers anddiastereomers. “Tert”, “^(t)”, and “t-” each refer to tertiary. “US”refers to the United States of America.

As used herein the term “alkylene” means a straight or branched chaindivalent hydrocarbon radical, preferably having from one to six carbonatoms (C₁₋₆alkylene). In some embodiments, the alkylene group has fromone to four carbon atoms (C₁₋₄alkylene). Examples of “alkylene” as usedherein include, but are not limited to, methylene (—CH₂—), ethylene(—CH₂CH₂—), propylene (—CH₂CH₂CH₂—), and branched versions thereof suchas (—CH(CH₃)—), —CH₂CH(CH₃)— and the like.

“Halo” means chloro, bromo, fluoro, or iodo.

“Alkyl” means an aliphatic hydrocarbon group which may be straight orbranched having 1 to 15 carbon atoms in the chain. Preferred alkylgroups have 1 to 12 carbon atoms in the chain, and more preferably 1 to6 carbon atoms. Branched means that one or more lower alkyl groups suchas methyl, ethyl or propyl are attached to a linear alkyl chain. “Loweralkyl” means about 1 to about 4 carbon atoms in the chain which may bestraight or branched. Exemplary alkyl groups include methyl,fluoromethyl, difluoromethyl, trifluoromethyl, cyclopropylmethyl,cyclopentylmethyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl,n-pentyl, 3-pentyl, heptyl, octyl, nonyl, decyl and dodecyl; preferredare methyl, difluoromethyl and i-propyl. Alkyl groups may be optionallysubstituted with one or more groups selected from halo, cyano, hydroxyl,carboxy, alkoxy, alkoxycarbonyl, oxo, amino, alkylamino, dialkylamino,cycloheteroalkyl, alkylcycloheteroalkyl, aryl, alkylaryl, heteroaryl,and alkylheteroaryl. Typically any alkyl or alkoxy moiety of the alkylsubstituent group has 1 to 6 carbon atoms.

“Aryl” means an aromatic carbocyclic radical containing 6 to 10 carbonatoms. Exemplary aryl groups include phenyl or naphthyl. Aryl groups maybe optionally substituted with one or more groups which may be the sameor different, and which are selected from alkyl, aryl, aralkyl, alkoxy,aryloxy, aralkyloxy, halo, and nitro. Typically any alkyl or alkoxymoiety of the aryl substituent group has 1 to 6 carbon atoms.

“Heteroaryl” means a 5- to a 10-membered aromatic monocyclic ormulticyclic hydrocarbon ring system in which one or more of the carbonatoms in the ring system is or are element(s) other than carbon, forexample nitrogen, oxygen or sulfur. Heteroaryl groups may be optionallysubstituted with one or more groups which may be the same or different,and which are selected from alkyl, aryl, aralkyl, alkoxy, aryloxy,aralkyloxy, halo, and nitro. Exemplary heteroaryl groups includepyrazinyl, furanyl, thienyl, pyridyl, pyrimidinyl, isoxazolyl,isothiazolyl, pyridazinyl, 1,2,4-triazinyl, quinolinyl, andisoquinolinyl.

“Aralkyl” means an aryl-alkyl group in which the aryl and alkylcomponents are as previously described. Preferred aralkyls contain alower alkyl moiety. Exemplary aralkyl groups include benzyl and2-phenethyl.

“Heteroaralkyl” means a heteroaryl-alkyl group in which the heteroaryland alkyl components are as previously described.

“Cycloalkyl” means a non-aromatic mono-, multicyclic, or bridged ringsystem of 3 to 10 carbon atoms. The cycloalkyl group is optionallysubstituted by one or more halo, or alkyl. Exemplary monocycliccycloalkyl rings include cyclopentyl, fluorocyclopentyl, cyclohexyl andcycloheptyl.

“Heterocycloalkyl” means a non-aromatic mono-, bi- or tricyclic, orbridged hydrocarbon ring system in which one or more of the atoms in thering system is or are element(s) other than carbon, for examplenitrogen, oxygen or sulfur. Preferred heterocycloalkyl groups containrings with a ring size of 3-6 ring atoms. Exemplary heterocycloalkylgroups pyrrolidine, piperidine, tetrahydropyran, tetrahydrofuran,tetrahydrothiopyran, and tetrahydrothiofuran.

“Cycloalkylalkyl” means a group in which the cycloalkyl and alkylcomponents are as previously described.

“Heteroycloalkylalkyl” means a group in which the cycloalkyl and alkylcomponents are as previously described.

The term “optionally substituted with deuterium” means that one or morehydrogen atoms in the referenced moiety or compound may be replaced witha corresponding number of deuterium atoms.

Throughout this specification, a variable may be referred to generally(e.g., “each R”) or may be referred to specifically (e.g., R¹, R², R³,etc.). Unless otherwise indicated, when a variable is referred togenerally, it is meant to include all specific embodiments of thatparticular variable.

Therapeutic Compounds

The present invention provides a compound of Formula A:

or a pharmaceutically acceptable salt thereof, wherein:

R¹ and R² are each independently selected from hydrogen, —(C₁-C₄)alkyl,or —(C₁-C₄)alkylene-O—(C₁-C₂)alkyl, wherein the alkyl and alkylenegroups at each instance are independently and optionally substitutedwith deuterium;

R³ is selected from —CH₃, —CH₂D, —CHD₂ and —CD₃;

R⁴ is n-butylene optionally substituted with deuterium;

R⁵ is selected from hydrogen, deuterium, alkyl, cycloalkyl,heterocycloalkyl, cycloalkylalkyl, heterocycloalkylalkyl, aryl, andheteroaryl, wherein each of the alkyl, cycloalkyl, heterocycloalkyl,cycloalkylalkyl, heterocycloalkylalkyl, aryl, and heteroaryl isoptionally substituted and wherein one or more hydrogen atoms in thealkyl, cycloalkyl, heterocycloalkyl, cycloalkylalkyl,heterocycloalkylalkyl, aryl, or heteroaryl or optional substituentthereof is optionally replaced with a corresponding number of deuteriumatoms; and

either (a) Y¹ and Y² are each fluorine, or are taken together with thecarbon to which they are bound to form C═O or (b) Y¹ is selected fromfluorine and OH; and Y² is selected from hydrogen, deuterium, —CH₃,—CH₂D, —CHD₂ and —CD₃; with the provisos that:

when Y¹ and Y² are taken together with the carbon to which they arebound to form C═O, then at least one of R¹, R², R³, R⁴, and R⁵ bears atleast one deuterium atom; and

when Y¹ is OH and Y² is hydrogen or CH₃, then at least one of R¹, R²,R³, R⁴ and R⁵ bears at least one deuterium atom.

In another embodiment, the compound of Formula A is other than thefollowing:

In another embodiment of Formula A, when R¹ and R² are each methyloptionally substituted with deuterium and R⁵ is hydrogen or deuterium,then either: (i) Y¹ is fluoro; (ii) Y¹ is OH, and Y² is selected from—CH₃, —CH₂D, —CHD₂ and —CD₃.

In one aspect of this embodiment, the compound is not

In a more specific aspect of this embodiment, at least one of Y², R¹,R², R³, and R⁴ bears at least one deuterium atom.

In still another embodiment of Formula A, R¹ and R² are each methyloptionally substituted with deuterium; R⁵ is hydrogen or deuterium; andeither: (a) Y¹ and Y² are taken together with the carbon atom to whichthey are bound to form ═O, or (b) Y¹ is —OH and Y² is selected fromhydrogen and deuterium, with the provisos that:

when Y¹ and Y² are taken together with the carbon to which they arebound to form C═O, then at least one of R¹, R², R³, R⁴, and R⁵ bears atleast one deuterium atom; and

when Y¹ is OH, then at least one of Y², R¹, R², R³, R⁴ and R⁵ bears atleast one deuterium atom.

In another embodiment of Formula A, R⁵ is D, the compound having FormulaA1:

or a salt thereof, wherein R¹, R², R³, R⁴, Y¹ and Y² are as defined forFormula A.

In one aspect of Formula A1, R¹ and R² are each independently selectedfrom —CH₃, —CH₂D, —CHD₂ and —CD₃; R³ is selected from —CH₃, —CH₂D, —CHD₂and —CD₃; R⁴ is selected from —(CH₂)₄—, —(CD₂)₄—, ∀—(CD₂)₃CH₂, and∀-CD₂(CH₂)₃—, wherein “∀” represents the portion of the R⁴ moiety boundto C(Y¹)(Y²) in the compound; and either (a) Y¹ is OH and Y² is selectedfrom hydrogen and deuterium; or (b) Y¹ and Y² are taken together withthe carbon to which they are attached to form C═O.

In a more specific aspect of Formula A1, R¹ and R² are eachindependently selected from —CH₃ and —CD₃; R³ is selected from —CH₃ and—CD₃; R⁴ is selected from —(CH₂)₄— and ∀-CD₂(CH₂)₃—; and either (a) Y¹is OH and Y² is selected from hydrogen and deuterium; or (b) Y¹ and Y²are taken together with the carbon to which they are attached to formC═O.

In another aspect of Formula A1, R¹ and R² are each independentlyselected from —CH₃ and —CD₃; R³ is selected from —CH₃ and —CD₃; R⁴ isselected from —(CH₂)₄— and ∀-CD₂(CH₂)₃—; and Y¹ and Y² are takentogether with the carbon to which they are attached to form C═O.

In another embodiment, the present invention provides a compound ofFormula A, wherein R⁵ is hydrogen, the compound having Formula I:

or a salt thereof, wherein:

R¹ and R² are each independently selected from hydrogen, —(C₁-C₄)alkyl,or —(C₁-C₄)alkylene-O—(C₁-C₂)alkyl, wherein the alkyl and alkylenegroups at each instance are independently and optionally substitutedwith deuterium;

R³ is selected from —CH₃, —CH₂D, —CHD₂ and —CD₃;

R⁴ is n-butylene optionally substituted with deuterium; and

either (a) Y¹ and Y² are each fluorine, or taken together with thecarbon to which they are attached, form C═O; or (b) Y¹ is selected fromfluorine and OH; and Y² is selected from hydrogen, deuterium, —CH₃,—CH₂D, —CHD₂ and —CD₃, with the provisos that:

when Y¹ and Y² are taken together with the carbon to which they areattached to form C═O at least one of R¹, R², R³ and R⁴ bears at leastone deuterium atom; and

when Y¹ is OH and Y² is hydrogen or —CH₃, then at least one of R¹, R²,R³ and R⁴ bears at least one deuterium atom.

In a more specific embodiment of Formula I, R¹ and R² are eachindependently selected from —CH₃, —CH₂D, —CHD₂ and —CD₃; R³ is selectedfrom —CH₃, —CH₂D, —CHD₂ and —CD₃; R⁴ is selected from —(CH₂)₄—,—(CD₂)₄—, ∀-(CD₂)₃CH₂, and ∀-CD₂(CH₂)₃—, wherein “∀” represents theportion of the R⁴ moiety bound to C(Y¹)(Y²) in the compound; and either:Y¹ is OH and Y² is selected from hydrogen and deuterium; or Y¹ and Y²are taken together with the carbon to which they are attached to formC═O.

In another aspect of Formula I, R¹ and R² are each independentlyselected from —CH₃ and —CD₃; R³ is selected from —CH₃ and —CD₃; R⁴ isselected from —(CH₂)₄— and ∀-CD₂(CH₂)₃—; and either: Y¹ is OH and Y² isselected from hydrogen and deuterium; or Y¹ and Y² are taken togetherwith the carbon to which they are attached to form C═O.

In another aspect of Formula I, R¹ and R² are each independentlyselected from —CH₃ and —CD₃; R³ is selected from —CH₃ and —CD₃; R⁴ isselected from —(CH₂)₄— and ∀-CD₂(CH₂)₃—; and Y¹ and Y² are takentogether with the carbon to which they are attached to form C═O.

In another embodiment, in any of the aspects set forth above, thecompound of Formula I is other than the following:

In yet another embodiment, in any of the aspects set forth above, thecompound of Formula I is other than the following:

In yet another embodiment, in any of the aspects set forth above, thecompound of Formula I is other than the following:

Another embodiment of the present invention provides a compound ofFormula II:

or a salt thereof, wherein:

R¹ and R² are each independently selected from hydrogen, —(C₁-C₄)alkyl,or —(C₁-C₄)alkylene-O—(C₁-C₂)alkyl, wherein the alkyl and alkylenegroups at each instance are independently and optionally substitutedwith deuterium;

R³ is selected from —CH₃, —CH₂D, —CHD₂ and —CD₃;

R⁴ is n-butylene optionally substituted with deuterium; and

wherein at least one of R², R³ and R⁴ bears at least one deuterium atom.

One embodiment relates to a compound of Formula A, A1, I, or II, whereinR² and R³ are each independently selected from —CH₃, —CH₂D, —CHD₂ and—CD₃.

Another embodiment relates to a compound of Formula A, A1, I, or II,wherein R² and R³ are each independently selected from —CH₃, and —CD₃.

Another embodiment relates to a compound of Formula A, A1, I, or II,wherein R¹ is selected from hydrogen, (C₁-C₃)alkyl, and(C₁-C₂)alkylene-O(C₁-C₂)alkyl.

Another embodiment relates to a compound of Formula A, A1, I, or II,wherein R¹ is hydrogen, —CH₃, —CD₃, —CH₂CH₂CH₃, —CD₂CH₂CH₃, —CD₂CD₂CH₃,—CD₂CD₂CD₃, —CH₂OCH₂CH₃, —CH₂OCD₂CH₃, —CH₂OCD₂CD₃, —CD₂OCH₂CH₃,—CD₂OCD₂CH₃, or —CD₂OCD₂CD₃.

Another embodiment relates to a compound of Formula A, wherein R⁵ isselected from hydrogen, deuterium, alkyl, cycloalkyl, heterocycloalkyl,cycloalkylalkyl, and heterocycloalkylalkyl, wherein each of alkyl,cycloalkyl, heterocycloalkyl, cycloalkylalkyl, and heterocycloalkylalkylmay be optionally substituted.

In other embodiments of Formula A, A1 or I:

-   -   a) each methylene unit in R⁴ is selected from —CH₂— and —CD₂-;        more specifically R⁴ is selected from —(CH₂)₄—, —(CD₂)₄—,        ^(∀)-CD₂(CH₂)₃— and ^(∀)-(CD₂)₃CH₂—, wherein “^(∀)” represents        the point where R⁴ is attached to C(Y¹)(Y²) in the compound;    -   b) when Y¹ is F, Y² is selected from hydrogen, —CH₃, —CH₂D,        —CHD₂ and —CD₃; or    -   c) when Y¹ is F, Y² fluorine; or    -   d) when Y¹ and Y² are not the same and Y² and R³ are not the        same and Y¹ and R³ are not the same, the stereochemistry at “*”        is represented by:

or

-   -   e) when Y¹ and Y² are not the same and Y² and R³ are not the        same and Y¹ and R³ are not the same, the stereochemistry at “*”        is represented by:

In other embodiments of Formula A, A1 or I, R¹ is —CD₃; R² and R³ are—CH₃; Y¹ and Y² are taken together to form C═O and R⁴ is selected from—(CH₂)₄—, —(CD₂)₄—, ^(∀)-CD₂(CH₂)₃— and ^(∀)-(CD₂)₃CH₂—.

In other embodiments of Formula A, A1 or I, R¹ is —CD₃; R² and R³ are—CH₃; Y¹ and Y² are taken together to form C═O and R⁴ is selected from—(CH₂)₄—, and —(CD₂)₄—.

In other embodiments of Formula A, A1 or I, R¹ is —CD₃; R² and R³ are—CH₃; R⁴ is —(CH₂)₄—; Y¹ is fluoro; and Y² is selected from deuterium,—CH₂D, —CHD₂ and —CD₃.

In other embodiments of Formula A, A1 or I, R¹ is —CD₃; R² and R³ are—CH₃; R⁴ is —(CH₂)₄—; Y¹ is fluoro; and Y² is fluorine.

In other embodiments of Formula A or A1, R¹ is —CD₃; R² and R³ are —CH₃;R⁴ is —(CH₂)₄—; R⁵ is deuterium; Y¹ is fluoro; and Y² is selected fromdeuterium, —CH₂D, —CHD₂ and —CD₃.

In other embodiments of Formula A or A1, R¹ is —CD₃; R² and R³ are —CH₃;R⁴ is —(CH₂)₄—; R⁵ is deuterium; Y¹ is fluoro; and Y² is fluorine.

In other embodiments of Formula A, A1 or I, Y¹ is F; Y² is selected fromhydrogen; R³ is —CH₃; and R⁴ is —(CH₂)₄—.

In other embodiments of Formula A, A1 or I, Y¹ is F; Y² is fluorine; R³is —CH₃; and R⁴ is —(CH₂)₄—.

One embodiment provides a compound of Formula B:

or a pharmaceutically acceptable salt thereof, wherein each of R¹ and R²is independently selected from —CH₃ and —CD₃; R⁵ is hydrogen ordeuterium; each Z³ is hydrogen or deuterium; each Z⁴ is hydrogen ordeuterium; each Z⁵ is hydrogen or deuterium; and either (a) Y¹ is OH,and Y² is hydrogen or deuterium, or (b) Y¹ and Y² are taken togetherwith the carbon to which they are attached to form C═O.

One embodiment provides a compound of Formula B, wherein each Z³, Z⁴ andZ⁵ is hydrogen. In one aspect, R¹ and R² are each —CD₃. In anotheraspect R⁵ is deuterium. In another aspect, Y¹ and Y² are taken togetherwith the carbon to which they are attached to form C═O. In still anotheraspect, Y¹ and is OH, and Y² is hydrogen or deuterium.

Another embodiment provides a compound of Formula B, wherein each Z³, Z⁴and Z⁵ is deuterium. In one aspect, R¹ and R² are each —CD3. In anotheraspect R⁵ is deuterium. In another aspect, Y¹ and Y² are taken togetherwith the carbon to which they are attached to form C═O. In still anotheraspect, Y¹ and is OH, and Y² is hydrogen or deuterium.

Yet another embodiment provides a compound of Formula B, wherein R¹ andR² are each —CD₃. In one aspect, R⁵ is deuterium. In another aspect,each Z³, Z⁴ and Z⁵ is hydrogen and R⁵ is deuterium. In another aspect,each Z³, Z⁴ and Z⁵ is deuterium and R⁵ is deuterium.

A further embodiment provides a compound of Formula B, wherein Y¹ and Y²are taken together with the carbon to which they are attached to formC═O. In one aspect, R⁵ is deuterium. In another aspect, each Z³, Z⁴ andZ⁵ is hydrogen and R⁵ is deuterium. In another aspect, each Z³, Z⁴ andZ⁵ is deuterium and R⁵ is deuterium. In another aspect, R¹ and R² areeach —CD₃. In another aspect, R¹ and R² are each —CD₃ and R⁵ isdeuterium. In another aspect, R¹ and R² are each —CD₃, and each Z³, Z⁴and Z⁵ is deuterium. In another aspect, R¹ and R² are each —CD₃, eachZ³, Z⁴ and Z⁵ is deuterium and R⁵ is deuterium. In another aspect, R¹and R² are each —CD₃, and each Z³, Z⁴ and Z⁵ is hydrogen. In anotheraspect, R¹ and R² are each —CD₃, each Z³, Z⁴ and Z⁵ is hydrogen and R⁵is deuterium

A still further embodiment provides a compound of Formula B, Y¹ and isOH, and Y² is hydrogen or deuterium. In one aspect, R⁵ is deuterium. Inanother aspect, each Z³, Z⁴ and Z⁵ is hydrogen and R⁵ is deuterium. Inanother aspect, each Z³, Z⁴ and Z⁵ is deuterium and R⁵ is deuterium. Inanother aspect, R¹ and R² are each —CD₃. In another aspect, R¹ and R²are each —CD₃ and R⁵ is deuterium. In another aspect, R¹ and R² are each—CD₃, and each Z³, Z⁴ and Z⁵ is deuterium. In another aspect, R¹ and R²are each —CD₃, each Z³, Z⁴ and Z⁵ is deuterium and R⁵ is deuterium. Inanother aspect, R¹ and R² are each —CD₃, and each Z³, Z⁴ and Z⁵ ishydrogen. In another aspect, R¹ and R² are each —CD₃, each Z³, Z⁴ and Z⁵is hydrogen and R⁵ is deuterium

Another embodiment provides a compound of Formula B, wherein R⁵ isdeuterium.

Another embodiment provides a compound of Formula B, wherein R⁵ isdeuterium, Z³, Z⁴ and Z⁵ is hydrogen and R¹ is —CD₃.

Specific examples of compounds of Formula A, A1, I, or II include thoseshown in Tables 1-6 (below) or pharmaceutically acceptable saltsthereof, wherein “^(∀)” represents the portion of the R⁴ moiety bound toC(Y¹)(Y²) in the compound. In the tables, compounds designated as “(R)”or “(S)” refer to the stereochemistry at the carbon bearing the Y¹substituent. Compounds lacking either designation and containing achiral carbon atom bound to Y¹ and Y² are intended to represent aracemic mixture of enantiomers.

TABLE 1 Examples of Specific Compounds of Formula I. Deuterated and/orFluorinated Analogs of Pentoxifylline and its Metabolites. Compound R¹R² R³ R⁴ Y¹ Y² 100 CD₃ CH₃ CH₃ (CH₂)₄ taken together as = O 101 CD₃ CD₃CH₃ (CH₂)₄ taken together as = O 102 CH₃ CD₃ CH₃ (CH₂)₄ taken togetheras = O 103 CD₃ CD₃ CD₃ (CD₂)₄ taken together as = O 104 CH₃ CH₃ CD₃(CD₂)₄ taken together as = O 105 CD₃ CH₃ CD₃ (CD₂)₄ taken together as =O 106 CH₃ CD₃ CD₃ (CD₂)₄ taken together as = O 107 CH₃ CH₃ CD₃^(†)CD₂(CH₂)₃ taken together as = O 108 CH₃ CH₃ CD₃ ^(†)(CD₂)₃CH₂ takentogether as = O 109 CD₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ taken together as = O 110CD₃ CH₃ CD₃ ^(†)(CD₂)₃CH₂ taken together as = O 111 CH₃ CD₃ CD₃^(†)CD₂(CH₂)₃ taken together as = O 112 CH₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ takentogether as = O 113 CD₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ taken together as = O 114CD₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ taken together as = O 115 CD₃ CD₃ CH₃ (CH₂)₄OH H 116 CD₃ CH₃ CH₃ (CH₂)₄ OH H 117 CH₃ CD₃ CH₃ (CH₂)₄ OH H 118 CD₃ CD₃CD₃ ^(†)CD₂(CH₂)₃ OH H 119 CD₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ OH H 119(R) CD₃ CH₃CD₃ ^(†)CD₂(CH₂)₃ (R)OH H 120 CH₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ OH H 121 CH₃ CH₃CD₃ ^(†)CD₂(CH₂)₃ OH H 122 CD₃ CD₃ CD₃ (CD₂)₄ OH H 123 CD₃ CH₃ CD₃(CD₂)₄ OH H 124 CH₃ CD₃ CD₃ (CD₂)₄ OH H 125 CH₃ CH CD₃ (CD₂)₄ OH H 126CD₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ OH H 127 CD₃ CH₃ CD₃ ^(†)(CD₂)₃CH₂ OH H 128CH₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ OH H 129 CH₃ CH₃ CD₃ ^(†)(CD₂)₃CH₂ OH H 130CD₃ CD₃ CH₃ (CH₂)₄ OH D 131 CD₃ CH₃ CH₃ (CH₂)₄ OH D 131(R) CD₃ CH₃ CH₃(CH₂)₄ (R)OH D 131(S) CD₃ CH₃ CH₃ (CH₂)₄ (S)OH D 132 CH₃ CD₃ CH₃ (CH₂)₄OH D 133 CH₃ CH₃ CH₃ (CH₂)₄ OH D 133(R) CH₃ CH₃ CH₃ (CH₂)₄ (R)OH D133(S) CH₃ CH₃ CH₃ (CH₂)₄ (S)OH D 134 CD₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ OH D 135CD₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ OH D 135(R) CD₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ (R)OH D136 CH₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ OH D 137 CH₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ OH D138 CD₃ CD₃ CD₃ (CD₂)₄ OH D 139 CD₃ CH₃ CD₃ (CD₂)₄ OH D 140 CH₃ CD₃ CD₃(CD₂)₄ OH D 141 CH₃ CH₃ CD₃ (CD₂)₄ OH D 142 CD₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ OHD 143 CD₃ CH₃ CD₃ ^(†)(CD₂)₃CH₂ OH D 144 CH₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ OH D145 CH₃ CH₃ CD₃ ^(†)(CD₂)₃CH₂ OH D 146 CD₃ CD₃ CH₃ (CH₂)₄ F H 147 CD₃CH₃ CH₃ (CH₂)₄ F H 148 CH₃ CD₃ CH₃ (CH₂)₄ F H 149 CH₃ CH₃ CH₃ (CH₂)₄ F H150 CD₃ CD₃ CH₃ (CH₂)₄ F F 151 CD₃ CH₃ CH₃ (CH₂)₄ F F 152 CH₃ CD₃ CH₃(CH₂)₄ F F 153 CH₃ CH₃ CH₃ (CH₂)₄ F F

Table 1 above shows examples of specific compounds of Formula I. Theseexamples are deuterated and/or fluorinated analogs of pentoxifylline andits metabolites.

TABLE 2 Examples of Specific Compounds of Formula I Where R¹ is H and Y²is CH₃ or CD₃. Compound R¹ R² R³ R⁴ Y¹ Y² 200 H CD₃ CH₃ (CH₂)₄ OH CH₃201 H CD₃ CD₃ (CH₂)₄ OH CD₃ 202 H CH₃ CD₃ (CH₂)₄ OH CD₃ 203 H CD₃ CD₃^(†)CD₂(CH₂)₃ OH CD₃ 204 H CH₃ CD₃ ^(†)CD₂(CH₂)₃ OH CD₃ 205 H CD₃ CD₃(CD₂)₄ OH CD₃ 206 H CH₃ CD₃ (CD₂)₄ OH CD₃ 207 H CD₃ CH₃ (CH₂)₄ F CH₃ 208H CH₃ CH₃ (CH₂)₄ F CH₃ 209 H CD₃ CD₃ (CD₂)₄ F CD₃ 210 H CH₃ CD₃ (CD₂)₄ FCD₃

Table 2 above shows examples of specific compounds of Formula I where R¹is H and Y² is CH₃ or CD₃. These compounds include deuterated andfluorinated analogs of Albifylline (HWA-138). Albifylline has beenstudied for uses that are associated with pentoxifylline.

TABLE 3 Specific Examples of Formula I Where R¹ is —CH₂—O—CH₂CH₃Optionally Substituted with Deuterium. Compound R¹ R² R³ R⁴ Y¹ Y² 250CD₂OCD₂CD₃ CD₃ CH₃ (CH₂)₄ OH CH₃ 251 CD₂OCH₂CH₃ CD₃ CH₃ (CH₂)₄ OH CH₃252 CH₂OCH₂CH₃ CD₃ CH₃ (CH₂)₄ OH CH₃ 253 CD₂OCD₂CD₃ CH₃ CH₃ (CH₂)₄ OHCH₃ 254 CD₂OCH₂CH₃ CH₃ CH₃ (CH₂)₄ OH CH₃ 255 CD₂OCD₂CD₃ CD₃ CD₃ (CH₂)₄OH CD₃ 256 CD₂OCH₂CH₃ CD₃ CD₃ (CH₂)₄ OH CD₃ 257 CH₂OCH₂CH₃ CD₃ CD₃(CH₂)₄ OH CD₃ 258 CD₂OCD₂CD₃ CH₃ CD₃ (CH₂)₄ OH CD₃ 259 CD₂OCH₂CH₃ CH₃CD₃ (CH₂)₄ OH CD₃ 260 CH₂OCH₂CH₃ CH₃ CD₃ (CH₂)₄ OH CD₃ 261 CD₂OCD₂CD₃CD₃ CD₃ ^(†)CD₂(CH₂)₃ OH CD₃ 262 CD₂OCH₂CH₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ OH CD₃263 CH₂OCH₂CH₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ OH CD₃ 264 CD₂OCD₂CD₃ CH₃ CD₃^(†)CD₂(CH₂)₃ OH CD₃ 265 CD₂OCH₂CH₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ OH CD₃ 266CH₂OCH₂CH₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ OH CD₃ 267 CD₂OCD₂CD₃ CD₃ CD₃ (CD₂)₄ OHCD₃ 268 CD₂OCH₂CH₃ CD₃ CD₃ (CD₂)₄ OH CD₃ 269 CH₂OCH₂CH₃ CD₃ CD₃ (CD₂)₄OH CD₃ 270 CD₂OCD₂CD₃ CH₃ CD₃ (CD₂)₄ OH CD₃ 271 CD₂OCH₂CH₃ CH₃ CD₃(CD₂)₄ OH CD₃ 272 CH₂OCH₂CH₃ CH₃ CD₃ (CD₂)₄ OH CD₃ 273 CD₂OCD₂CD₃ CD₃CH₃ (CH₂)₄ F CH₃ 274 CD₂OCH₂CH₃ CD₃ CH₃ (CH₂)₄ F CH₃ 275 CH₂OCH₂CH₃ CD₃CH₃ (CH₂)₄ F CH₃ 276 CD₂OCD₂CD₃ CH₃ CH₃ (CH₂)₄ F CH₃ 277 CD₂OCH₂CH₃ CH₃CH₃ (CH₂)₄ F CH₃ 278 CH₂OCH₂CH₃ CH₃ CH₃ (CH₂)₄ F CH₃ 279 CD₂OCD₂CD₃ CD₃CD₃ (CD₂)₄ F CD₃ 280 CD₂OCH₂CH₃ CD₃ CD₃ (CD₂)₄ F CD₃ 281 CH₂OCH₂CH₃ CD₃CD₃ (CD₂)₄ F CD₃ 282 CD₂OCD₂CD₃ CH₃ CD₃ (CD₂)₄ F CD₃ 283 CD₂OCH₂CH₃ CH₃CD₃ (CD₂)₄ F CD₃ 284 CH₂OCH₂CH₃ CH₃ CD₃ (CD₂)₄ F CD₃

Table 3 above shows examples of specific compounds of Formula I where R¹is —CH₂—O—CH₂CH₃, optionally substituted with deuterium. In theseexamples, Y¹ is OH or F and Y² is CH₃ or CD₃. These compounds includedeuterated and fluorinated analogs of torbafylline (HWA-448).Torbafylline has been studied for the treatment of depression, urinaryincontinence, irritable bowel syndrome and multiple sclerosis.

TABLE 4 Specific Examples of Formula I Where R¹ is —CH₂CH₂CH₃ OptionallySubstituted With Deuterium and Y¹ is OH or F. Compound R¹ R² R³ R⁴ Y¹ Y²300 CD₂CD₂CD₃ CD₃ CH₃ (CH₂)₄ OH CH₃ 301 CD₂CH₂CH₃ CD₃ CH₃ (CH₂)₄ OH CH₃302 CH₂CH₂CH₃ CD₃ CH₃ (CH₂)₄ OH CH₃ 303 CD₂CD₂CD₃ CH₃ CH₃ (CH₂)₄ OH CH₃304 CD₂CH₂CH₃ CH₃ CH₃ (CH₂)₄ OH CH₃ 305 CD₂CD₂CD₃ CD₃ CD₃ (CH₂)₄ OH CD₃306 CD₂CH₂CH₃ CD₃ CD₃ (CH₂)₄ OH CD₃ 307 CH₂CH₂CH₃ CD₃ CD₃ (CH₂)₄ OH CD₃308 CD₂CD₂CD₃ CH₃ CD₃ (CH₂)₄ OH CD₃ 309 CD₂CH₂CH₃ CH₃ CD₃ (CH₂)₄ OH CD₃310 CH₂CH₂CH₃ CH₃ CD₃ (CH₂)₄ OH CD₃ 311 CD₂CD₂CD₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃OH CD₃ 312 CD₂CH₂CH₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ OH CD₃ 313 CH₂CH₂CH₃ CD₃ CD₃^(†)CD₂(CH₂)₃ OH CD₃ 314 CD₂CD₂CD₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ OH CD₃ 315CD₂CH₂CH₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ OH CD₃ 316 CH₂CH₂CH₃ CH₃ CD₃^(†)CD₂(CH₂)₃ OH CD₃ 317 CD₂CD₂CD₃ CD₃ CD₃ (CD₂)₄ OH CD₃ 318 CD₂CH₂CH₃CD₃ CD₃ (CD₂)₄ OH CD₃ 319 CH₂CH₂CH₃ CD₃ CD₃ (CD₂)₄ OH CD₃ 320 CD₂CD₂CD₃CH₃ CD₃ (CD₂)₄ OH CD₃ 321 CD₂CH₂CH₃ CH₃ CD₃ (CD₂)₄ OH CD₃ 322 CH₂CH₂CH₃CH₃ CD₃ (CD₂)₄ OH CD₃ 323 CD₂CD₂CD₃ CD₃ CH₃ (CH₂)₄ F CH₃ 324 CD₂CH₂CH₃CD₃ CH₃ (CH₂)₄ F CH₃ 325 CH₂CH₂CH₃ CD₃ CH₃ (CH₂)₄ F CH₃ 326 CD₂CD₂CD₃CH₃ CH₃ (CH₂)₄ F CH₃ 327 CD₂CH₂CH₃ CH₃ CH₃ (CH₂)₄ F CH₃ 328 CH₂CH₂CH₃CH₃ CH₃ (CH₂)₄ F CH₃ 329 CD₂CD₂CD₃ CD₃ CD₃ (CD₂)₄ F CD₃ 330 CD₂CH₂CH₃CD₃ CD₃ (CD₂)₄ F CD₃ 331 CH₂CH₂CH₃ CD₃ CD₃ (CD₂)₄ F CD₃ 332 CD₂CD₂CD₃CH₃ CD₃ (CD₂)₄ F CD₃ 333 CD₂CH₂CH₃ CH₃ CD₃ (CD₂)₄ F CD₃ 334 CH₂CH₂CH₃CH₃ CD₃ (CD₂)₄ F CD₃

Table 4 above shows examples of specific compounds of Formula I where R¹is —CH₂CH₂CH₃ optionally substituted with deuterium. In these examples,Y¹ is OH or F and Y² is CH₃ or CD₃. These compounds include deuteratedand fluorinated analogs of A-802715. A-802715 has been studied for thetreatment of septic shock and inhibition of effects of allograftreaction.

TABLE 5 Specific Examples of Formula I where R¹ is —CH₂CH₂CH₃ OptionallySubstituted With Deuterium and Y¹ and Y² Are Taken Together As = OCompound R¹ R² R³ R⁴ Y¹ Y² 350 CD₂CD₂CD₃ CD₃ CH₃ (CH₂)₄ taken togetheras = O 351 CD₂CH₂CH₃ CD₃ CH₃ (CH₂)₄ taken together as = O 352 CH₂CH₂CH₃CD₃ CH₃ (CH₂)₄ taken together as = O 353 CD₂CD₂CD₃ CH₃ CH₃ (CH₂)₄ takentogether as = O 354 CD₂CH₂CH₃ CH₃ CH₃ (CH₂)₄ taken together as = O 355CD₂CD₂CD₃ CD₃ CD₃ (CH₂)₄ taken together as = O 356 CD₂CH₂CH₃ CD₃ CD₃(CH₂)₄ taken together as = O 357 CH₂CH₂CH₃ CD₃ CD₃ (CH₂)₄ taken togetheras = O 358 CD₂CD₂CD₃ CH₃ CD₃ (CH₂)₄ taken together as = O 359 CD₂CH₂CH₃CH₃ CD₃ (CH₂)₄ taken together as = O 360 CH₂CH₂CH₃ CH₃ CD₃ (CH₂)₄ takentogether as = O 361 CD₂CD₂CD₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ taken together as =O 362 CD₂CH₂CH₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ taken together as = O 363CH₂CH₂CH₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ taken together as = O 364 CD₂CD₂CD₃ CH₃CD₃ ^(†)CD₂(CH₂)₃ taken together as = O 365 CD₂CH₂CH₃ CH₃ CD₃^(†)CD₂(CH₂)₃ taken together as = O 366 CH₂CH₂CH₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃taken together as = O 367 CD₂CD₂CD₃ CD₃ CD₃ (CD₂)₄ taken together as = O368 CD₂CH₂CH₃ CD₃ CD₃ (CD₂)₄ taken together as = O 369 CH₂CH₂CH₃ CD₃ CD₃(CD₂)₄ taken together as = O 370 CD₂CD₂CD₃ CH₃ CD₃ (CD₂)₄ taken togetheras = O 371 CD₂CH₂CH₃ CH₃ CD₃ (CD₂)₄ taken together as = O 372 CH₂CH₂CH₃CH₃ CD₃ (CD₂)₄ taken together as = O

Table 5 above shows examples of specific compounds of Formula I where R¹is —CH₂CH₂CH₃ optionally substituted with deuterium. In these examples,Y¹ and Y² are taken together with their intervening carbon to form acarbonyl. These compounds include deuterated analogs of propentofylline.Propentofylline has been studied for the treatment of Alzheimer'sdisease, neuropathic pain, traumatic brain injury, dysuria, retinal oroptic nerve head damage, and peptic ulcers. It has also been studied forcontrolling intraocular pressure, stabilization of auto-regulation ofcerebral blood flow and inhibition of effects of allograft reaction.

TABLE 6 Examples of Specific Compounds of Formula A. Deuterated and/orFluorinated Analogs of Pentoxifylline and its Metabolites where R⁵ is DCom- pound R¹ R² R³ R⁴ R⁵ Y¹ Y² 400 CD₃ CH₃ CH₃ (CH₂)₄ D Taken togetheras = O 401 CD₃ CD₃ CH₃ (CH₂)₄ D Taken together as = O 402 CH₃ CD₃ CH₃(CH₂)₄ D Taken together as = O 403 CD₃ CD₃ CD₃ (CD₂)₄ D Taken togetheras = O 404 CH₃ CH₃ CD₃ (CD₂)₄ D Taken together as = O 405 CD₃ CH₃ CD₃(CD₂)₄ D Taken together as = O 406 CH₃ CD₃ CD₃ (CD₂)₄ D Taken togetheras = O 407 CH₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ D Taken together as = O 408 CH₃ CH₃CD₃ ^(†)(CD₂)₃CH₂ D Taken together as = O 409 CD₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃D Taken together as = O 410 CD₃ CH₃ CD₃ ^(†)(CD₂)₃CH₂ D Taken togetheras = O 411 CH₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ D Taken together as = O 412 CH₃ CD₃CD₃ ^(†)(CD₂)₃CH₂ D Taken together as = O 413 CD₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃D Taken together as = O 414 CD₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ D Taken togetheras = O 415 CD₃ CD₃ CH₃ (CH₂)₄ D OH H 416 CD₃ CH₃ CH₃ (CH₂)₄ D OH H 417CH₃ CD₃ CH₃ (CH₂)₄ D OH H 418 CD₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ D OH H 419 CD₃CH₃ CD₃ ^(†)CD₂(CH₂)₃ D OH H 419(R) CD₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ D (R)OH H419(S) CD₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ D (S)OH H 420 CH₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃D OH H 421 CH₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ D OH H 422 CD₃ CD₃ CD₃ (CD₂)₄ D OHH 423 CD₃ CH₃ CD₃ (CD₂)₄ D OH H 424 CH₃ CD₃ CD₃ (CD₂)₄ D OH H 425 CH₃CH₃ CD₃ (CD₂)₄ D OH H 426 CD₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ D OH H 427 CD₃ CH₃CD₃ ^(†)(CD₂)₃CH₂ D OH H 428 CH₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ D OH H 429 CH₃CH₃ CD₃ ^(†)(CD₂)₃CH₂ D OH H 430 CD₃ CD₃ CH₃ (CH₂)₄ D OH D 431 CD₃ CH₃CH₃ (CH₂)₄ D OH D 432 CH₃ CD₃ CH₃ (CH₂)₄ D OH D 433 CH₃ CH₃ CH₃ (CH₂)₄ DOH D 434 CD₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ D OH D 435 CD₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃D OH D 435(R) CD₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ D (R)OH D 435(S) CD₃ CH₃ CD₃^(†)CD₂(CH₂)₃ D (S)OH D 436 CH₃ CD₃ CD₃ ^(†)CD₂(CH₂)₃ D OH D 437(R) CH₃CH₃ CD₃ ^(†)CD₂(CH₂)₃ D (R)OH D 437(S) CH₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ D (S)OHD 437 CH₃ CH₃ CD₃ ^(†)CD₂(CH₂)₃ D OH D 438 CD₃ CD₃ CD₃ (CD₂)₄ D OH D 439CD₃ CH₃ CD₃ (CD₂)₄ D OH D 440 CH₃ CD₃ CD₃ (CD₂)₄ D OH D 441 CH₃ CH₃ CD₃(CD₂)₄ D OH D 442 CD₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ D OH D 443 CD₃ CH₃ CD₃^(†)(CD₂)₃CH₂ D OH D 444 CH₃ CD₃ CD₃ ^(†)(CD₂)₃CH₂ D OH D 445 CH₃ CH₃CD₃ ^(†)(CD₂)₃CH₂ D OH D 446 CD₃ CD₃ CH₃ (CH₂)₄ D F H 447 CH₃ CH₃ CH₃(CH₂)₄ D F H 448 CD₃ CH₃ CH₃ (CH₂)₄ D F H 449 CH₃ CD₃ CH₃ (CH₂)₄ D F H450 CD₃ CD₃ CH₃ (CH₂)₄ D F F 451 CD₃ CH₃ CH₃ (CH₂)₄ D F F 452 CH₃ CD₃CH₃ (CH₂)₄ D F F 453 CH₃ CH₃ CH₃ (CH₂)₄ D F F

Table 6 above shows examples of specific compounds of Formula A. Theseexamples are deuterated and/or fluorinated analogs of pentoxifylline andits metabolites where R⁵ is deuterium.

In one aspect of the above embodiment, the compound is not any one ofCompounds 100, 116, or 149.

Examples of specific compounds of this invention include the following:

In another set of embodiments, any atom not designated as deuterium inany of the embodiments set forth above is present at its naturalisotopic abundance.

The synthesis of compounds of this invention can be achieved bysynthetic chemists of ordinary skill. Relevant procedures andintermediates are disclosed, for instance in Sidzhakova, D et al.,Farmatsiya, (Sofia, Bulgaria) 1988, 38(4): 1-5; Davis, P J et al.,Xenobiotica, 1985, 15(12): 1001-10; Akgun, H et al., J Pharm Sci, 2001,26(2): 67-71; German Patent publication DD 274334; Czech Patent Nos. CS237719, CS201558; PCT patent publication WO9531450; and in JapanesePatent publication Nos. JP58150594, JP58134092, JP58038284, JP57200391,JP57098284, JP57085387, JP57062278, JP57080385, JP57056481, JP57024385,JP57011981, JP57024386, JP57024382, JP56077279, JP56032477, JP56007785,JP56010188, JP56010187, JP55122779, and JP55076876.

Such methods can be carried out utilizing corresponding deuterated andoptionally, other isotope-containing reagents and/or intermediates tosynthesize the compounds delineated herein, or invoking standardsynthetic protocols known in the art for introducing isotopic atoms to achemical structure.

Exemplary Synthesis

Methods for synthesizing compounds of Formula I are depicted in thefollowing schemes.

As depicted in Scheme 1A, deuterated compound 10 is alkylated withdeuterated intermediate 11 (wherein X is chloride, bromide or iodide) inthe presence of potassium carbonate to afford compounds of Formula I.Alternatively, sodium hydroxide in aqueous methanol may be employed toafford compounds of Formula I according to the methods of U.S. Pat. No.4,289,776.

As depicted in Scheme 1B, compounds of Formula II can be used to makecompounds where Y¹ is OH. Thus, compounds of Formula II are reduced witheither sodium borohydride or sodium borodeuteride (commerciallyavailable at 99 atom % D) according to the general method of EuropeanPatent publication 0330031 to form compounds wherein Y¹ is OH and Y² ishydrogen or deuterium. The enantiomeric alcohol products may beseparated, for example through the method of Nicklasson, M et al.,Chirality, 2002, 14(8): 643-652. In an alternate method, enzymaticreduction affords an enantiomerically-enriched alcohol product using themethods disclosed in Pekala, E et al., Acta Poloniae Pharmaceutica,2007, 64(2): 109-113, or in Pekala, E et al., Biotech J, 2007, 2(4):492-496.

Synthesis of Compound 10

Referring to Scheme 1A, compounds that can be used as compound 10 tomake compounds of Formula I are known and include, but are not limitedto, the following: theobromine (wherein R¹ and R² are CH₃) which iscommercially available. Isotopologues of 10 wherein: (a) R¹ is —CD₃ andR² is —CH₃; (b) R¹ is —CH₃ and R² is —CD₃; and (c) R¹ and R² are —CD₃are all known. See Benchekroun, Y et al., J Chromatogr B, 1977, 688:245; Ribon, B et al., Coll INSERM, 1988, 164: 268; and Horning, M G etal., Proc Int Conf Stable Isot 2^(nd), 1976, 41-54.3-Methyl-7-propylxanthine, wherein R¹ is n-propyl and R² is —CH₃, iscommercially available. Compound 10 wherein R¹ is CH₂OCH₃ and R² is CH₃is also known. See German patent application DE 3942872A1.

A synthesis of compound 10 is depicted in Scheme 2 starting withcommercially-available N-nitroso-N-methylurea. Treatment withappropriately deuterated amine 12 in water affords N-alkylurea 13following the methods of Boivin, J L et al., Canadian Journal ofChemistry, 1951, 29: 478-81. Urea 13 may be treated with 2-cyanoaceticacid and acetic anhydride to provide cyanoacetamide derivative 14, whichis treated first with aqueous NaOH and then with aqueous HCl to providecyclized pyrimidinedione 15 according to the methods of Dubey, P K etal., Indian Journal of Heterocyclic Chemistry, 2005, 14(4): 301-306.Alternatively, cyanoacetamide 14 may be treated withtrimethylsilylchloride and hexamethyldisilazane to afford the cyclizedproduct 15 via the methods of Fulle, F et al., Heterocycles, 2000,53(2): 347-352.

Following the methods of Merlos, M et al., European Journal of MedicinalChemistry, 1990, 25(8): 653-8, treatment of pyrimidinedione 15 withsodium nitrite in acetic acid, and then by ammonium hydroxide and sodiumdithionite, yields compound 16, which is treated with formic acid toprovide purine derivative 17. Following the methods disclosed by Rybar,A et al., in Czech patent application CS 26359581, alkylation of 17 withappropriately deuterated electrophile 18 (X is chloro, bromo, or iodo)in the presence of potassium carbonate and optionally in the presence ofadditives such as NaBr, KBr, NaI, KI, or iodine, affords compound 10.

Referring to Scheme 2, useful deuterated amine reagents 12 include, butare not limited to, commercially-available compounds such asn-propyl-d₇-amine, or known compounds such as 1-propan-1,1-d₂-amine(Moritz, F et al., Organic Mass Spectrometry, 1993, 28(3): 207-15).Useful deuterated urea reagents 13 may include, but are not limited to,commercially-available compounds such as N-methyl-d₃-urea

or methylurea-d₆

Useful deuterated electrophiles 18 may include, but are not limited to,commercially-available compounds such as iodomethane-d₃, orbromomethane-d₃, or 1-bromopropane-d₇, or 1-bromopropane-1,1-d₂, orknown compounds such as (chloromethoxy-d₂)-ethane (Williams, AG, WO2002059070A1), or bromomethoxymethane-d₂ (Van der Veken, B J et al.,Journal of Raman Spectroscopy, 1992, 23(4): 205-23, or(bromomethoxy-d₂)-methane-d₃ (Van der Veken, B J et al., Journal ofRaman Spectroscopy, 1992, 23(4): 205-23. The commercially availabledeuterated intermediates 12, 13 and 18 mentioned above are availablehaving an isotopic purity of at least 98 atom % D.Synthesis of Intermediate 11a-d₅ (cf. Scheme 1A)

An approach to the preparation of compound 11a-d₅ (cf. Scheme 1A)(wherein R³ is CD₃; R⁴ is ^(∀)-CD₂(CH₂)₃—, and Y¹ and Y² are takentogether to form ═O), is depicted in Scheme 3. Thus, methyllithium isadded to commercially-available delta-valerolactone 19 according to theprocedure of Zhang, Q et al., Tetrahedron, 2006, 62(50): 11627-11634 toafford ketone 20. Treatment of 20 with TFA-d₁ (99 atom % D) in D₂O (99atom % D) under microwave conditions provides deuterated ketone 21according to the general method of Fodor-Csorba K, Tet Lett, 2002, 43:3789-3792. The alcohol moiety in 21 is converted to the chloride upontreatment with triphenylphosphine and carbon tetrachloride to yieldchloride 11a-d₅ following the general procedures of Clement, J-L, OrgBiomol Chem, 2003, 1: 1591-1597.

Scheme 4 depicts a synthesis of compound 11a-d₉ and compound 11a-d₁₁.Thus, commercially-available 4-phenylbutyric acid 22 may be heated inD₂O (99 atom % D) in the presence of Pd/C and hydrogen gas to afforddeuterated acid 23 according to the general methods of Esaki, et al.,Chem Eur J, 2007, 13: 4052-4063. Addition of deuterated methyllithium inthe presence of trimethylsilyl chloride provides ketone 24, according tothe general method of Porta, A et al., J Org Chem, 2005, 70(12):4876-4878. Ketone 24 is converted to acetal 25 by treatment with D₂SO₄(99 atom % D) and commercially-available ethyleneglycol-d₂ (99 atom %D). Treatment of 25 with NaIO₄ and RuCl₃ according to the general methodof Gamier, J-M et al., Tetrahedron: Asymmetry, 2007, 18(12): 1434-1442provides carboxylic acid 26. Reduction with either LiAlH₄ or LiAlD₄ (98atom % D) provides the alcohols (not shown), which are then chlorinatedusing either phosphorus oxychloride or triphenylphosphine andN-chlorosuccinimide (Naidu, S V et al., Tet Lett, 2007, 48(13):2279-2282), followed by acetal cleavage with D₂SO₄ (Heathcock, C H etal., J Org Chem, 1995, 60(5): 1120-30) to provides chlorides 11a-d₉ and11a-d₁₁, respectively.

Schemes 4a and 4b depict the synthesis of specific enantiomers ofchlorides 11b-(R) (wherein Y¹ is fluorine; Y² is selected from hydrogenand deuterium; and the compound is in the (R) configuration) and 11b-(S)(wherein Y¹ is fluorine; Y² is selected from hydrogen and deuterium; andthe compound is in the (S) configuration). In Scheme 4a, a deuterated(or nondeuterated) benzyl-protected alcohol 27, such as known[[[(5R)-5-fluorohexyl]oxy]methyl]-benzene (PCT publication WO2000031003)is deprotected by hydrogenation in the presence of Pd/C to providealcohol 28. The alcohol is chlorinated with thionyl chloride accordingto the general procedure of Lacan, G et al., J Label Compd Radiopharm,2005, 48(9): 635-643 to afford chloride 11b-(R).

In Scheme 4b, a deuterated (or nondeuterated) alcohol 29, such as known(S)-(+)-5-fluorohexanol (Riswoko, A et al., Enantiomer, 2002, 7(1):33-39) is chlorinated to afford chloride 11b-(S).

Scheme 5 depicts a synthesis of other intermediates 11c and 11e. Thus,following the methods of either Kutner, Andrzej et al., Journal ofOrganic Chemistry, 1988, 53(15): 3450-7, or of Larsen, S D et al.,Journal of Medicinal Chemistry, 1994, 37(15): 2343-51, compounds 30 or31 (wherein X is a halide) may be treated with deuterated Grignardreagent 32 to afford intermediate 11c wherein R³ and Y² are the same, Y¹is OH, and X is a halide. Treatment with diethylaminosulfur trifluoride(DAST) in dichloromethane or toluene provides intermediate 11e whereinR³ and Y² are the same, Y¹ is F, and X is a halide according to thegeneral procedures of either Karst, N A et al., Organic Letters, 2003,5(25): 4839-4842, or of Kiso, M et al., Carbohydrate Research, 1988,177: 51-67.

Commercially available halides can be used to make compounds 11 asdisclosed in Scheme 5. For example, commercially-available5-chlorovaleryl chloride, or commercially-available 5-bromovalerylchloride, or commercially-available ethyl 5-bromovalerate, may be usefulas reagents 30 or 31. Referring again to Scheme 5, use ofcommercially-available methyl-d₃-magnesium iodide as Grignard reagent 32affords electrophile 11 wherein R³ and Y² are simultaneously CD₃.

Scheme 6 depicts an alternate synthesis of intermediate 11e, wherein R³and Y² are the same and X═Br. Thus, according to the procedures ofHester, J B et al., Journal of Medicinal Chemistry, 2001, 44(7):1099-1115, commercially-available 4-chloro-1-butanol is protected viatreatment with 3,4-dihydro-2H-pyran (DHP) and camphorsulfonic acid (CSA)to provide chloride 33. Generation of the corresponding Grignard reagentwith magnesium, followed by addition of acetone (R³═Y²═CH₃) oracetone-d₆ (Y²═R³=CD₃), affords alcohol 34. Fluorination withdiethylaminosulfur trifluoride (DAST) in DCM provides fluoride 35.Deprotection with CSA in MeOH provides alcohol 36, and treatment withN-bromosuccinimide and triphenyl phosphine affords intermediate 11e.

Scheme 7 depicts the synthesis of intermediate 11e wherein R³ and Y² arethe same and X═Br. Thus, commercially-available 4-hydroxy-butanoic acidethyl ester 37 is treated with DHP and CSA, or with DHP, TsOH, andpyridine to provide ester 38. Reduction with LiAlD₄ affords deuteratedalcohol 39, which is treated with either triphenyl phosphine in CCl₄(Sabitha, G et al., Tetrahedron Letters, 2006, (volume date 2007),48(2): 313-315) or with methanesulfonyl chloride, lithium chloride, and2,6-lutidine in DMF (Blaszykowski, C et al., Organic Letters, 2004,6(21): 3771-3774) to afford chloride 40. Following the same methods asin Scheme 6, chloride 40 may be converted to 11e.

Scheme 8 depicts the synthesis of intermediate 11e-d₈ wherein R³ and Y²are the same and X═Br. Thus, commercially-available THF-d₈ 41 may betreated with DCl and ZnCl₂ according to the general methods of Yang, Aet al., Huagong Shikan, 2002, 16(3): 37-39 to afford known chloride 42(Alken, Rudolf-Giesbert, WO 2003080598A1). Following the same methods asin Scheme 6, chloride 42 may be converted to 11e-d₈.

Scheme 9 depicts the synthesis of intermediate 11c-d₈ wherein R³ and Y²are the same and X═Br. Thus, known carboxylic acid 43 (Lompa-Krzymien, Let al., Proc. Int. Conf. Stable Isot. 2^(nd), 1976, Meeting Date 1975,574-8) is treated with either diazomethane (according to the generalmethod of Garrido, N M et al., Molecules, 2006, 11(6): 435-443.) or withtrimethylsilyl chloride and methanol-d₁ (according to the general methodof Doussineau, T et al., Synlett, 2004, (10): 1735-1738) to providemethyl ester 44. As in Scheme 5, treatment of the ester with deuteratedGrignard reagent 45 affords intermediate 11c-d₈. For example, use ofcommercially-available methyl-d₃-magnesium iodide as Grignard reagent 45affords 11c-d₈ wherein R³ and Y² are simultaneously CD₃.

Scheme 10 depicts a preparation of 11c-d₂, wherein R³ and Y² are thesame. Thus, known deuterated ester 46 (Feldman, K S et al., Journal ofOrganic Chemistry, 2000, 65(25): 8659-8668) is treated with carbontetrabromide and triphenylphosphine (Brueckner, A M et al., EuropeanJournal of Organic Chemistry, 2003, (18): 3555-3561) to afford ester 47wherein X is bromide, or is treated with methanesulfonyl chloride andtriethylamine, followed by lithium chloride and DMF (Sagi, K et al.,Bioorganic & Medicinal Chemistry, 2005, 13(5): 1487-1496) to affordester 47 wherein X is chloride. As in Scheme 5, treatment of ester 47with deuterated Grignard reagent 48 affords 11c-d₂. For example, use ofcommercially-available methyl-d₃-magnesium iodide as Grignard reagent 48affords 11c-d₂ wherein R³ and Y² are simultaneously CD₃.

Additional known chlorides that may be utilized as reagent 11 in Scheme1A include: 1-chloro-5,5-difluoro-hexane (Rybczynski, P J et al., J MedChemistry, 2004, 47(1): 196-209); 1-chloro-5-fluorohexane (Chambers, R Det al., Tetrahedron, 2006, 62(30): 7162-7167); 6-chloro-2-hexanol(European Patent publication 0412596); (S)-6-chloro-2-hexanol (Keinan, Eet al., J Am Chem Soc, 1986, 108(12): 3474-3480); commercially-available(R)-6-chloro-2-hexanol; commercially available 6-chloro-2-hexanone;known 6-chloro-2-methylhexan-2-ol (Kutner, A et al., Journal of OrganicChemistry, 1988, 53(15): 3450-7); known 6-bromo-2-methylhexan-2-ol(Kutner, A et al., Journal of Organic Chemistry, 1988, 53(15): 3450-7);known 1-bromo-5-fluoro-5-methylhexane (Hester, J B et al., Journal ofMedicinal Chemistry, 2001, 44(7): 1099-1115).

Scheme 11 depicts the synthesis of a compound of Formula A1. Thus, acompound of Formula I is treated with potassium carbonate in D₂O toeffect a hydrogen-to-deuterium exchange reaction, providing a compoundof Formula A1. One skilled in the art will appreciate that additionalhydrogen-to-deuterium exchange reactions may also occur elsewhere in themolecule.

An alternative synthesis of a compound of Formula A1 is depicted inScheme 12. Thus, intermediate 10 (cf. Scheme 1A) is treated withpotassium carbonate in D₂O to effect a hydrogen-to-deuterium exchangereaction, providing compound 50 as either the N-D or N-H species.Alkylation with intermediate 11 in the presence of potassium carbonateaffords compounds of Formula A1.

A number of novel intermediates can be used to prepare compounds ofFormula A. Thus, the invention also provides such a compound which isselected from the following:

Compounds a-d above may be prepared as generally described in Org.Lett., 2005, 7: 1427-1429 using appropriately-deuterated startingmaterials. Compounds e-o may be prepared from the appropriate bromideslisted above by reference to Scheme 15 shown below.

Certain xanthine intermediates useful for this invention are also novel.Thus, the invention provides a deuterated xanthine intermediate III:

where W is hydrogen or deuterium, and each of R¹ and R² is independentlyselected from hydrogen, deuterium, C₁₋₃ alkyl optionally substitutedwith deuterium, and C₁₋₃ alkoxyalkyl optionally substituted withdeuterium. Examples of R¹ and R²C₁₋₃ alkyl include —CH₃, —CD₃,—CH₂CH₂CH₃, and —CD₂CD₂CD₃. Examples of C₁₋₃ alkoxyalkyl include—CH₂OCH₂CH₃, —CD₂OCH₂CH₃, —CD₂OCD₂CH₃, and —CD₂OCD₂CD₃.

Specific examples of formula III include the following:

In each of the above examples of formula III, W is hydrogen. In a set ofcorresponding examples, W is deuterium. Salts of compounds of FormulaIII are also useful, including salts that are known to be useful withrespect to known xanthines. Examples of useful salts include, but arenot limited to, the lithium salt, sodium salt, potassium salt, andcesium salt. An example of a particularly useful salt is the potassiumsalt.

The specific approaches and compounds shown above are not intended to belimiting. The chemical structures in the schemes herein depict variablesthat are hereby defined commensurately with chemical group definitions(moieties, atoms, etc.) of the corresponding position in the compoundformulae herein, whether identified by the same variable name (i.e., R¹,R², R³, etc.) or not. The suitability of a chemical group in a compoundstructure for use in the synthesis of another compound is within theknowledge of one of ordinary skill in the art.

Additional methods of synthesizing compounds of this invention and theirsynthetic precursors, including those within routes not explicitly shownin schemes herein, are within the means of chemists of ordinary skill inthe art. Synthetic chemistry transformations and protecting groupmethodologies (protection and deprotection) useful in synthesizing theapplicable compounds are known in the art and include, for example,those described in Larock R, Comprehensive Organic Transformations, VCHPublishers (1989); Greene T W et al., Protective Groups in OrganicSynthesis, 3^(rd) Ed., John Wiley and Sons (1999); Fieser L et al.,Fieser and Fieser's Reagents for Organic Synthesis, John Wiley and Sons(1994); and Paquette L, ed., Encyclopedia of Reagents for OrganicSynthesis, John Wiley and Sons (1995) and subsequent editions thereof.

Combinations of substituents and variables envisioned by this inventionare only those that result in the formation of stable compounds.

Compositions

The invention also provides pyrogen-free compositions comprising aneffective amount of a compound of this invention or pharmaceuticallyacceptable salts thereof; and an acceptable carrier. Preferably, acomposition of this invention is formulated for pharmaceutical use (“apharmaceutical composition”), wherein the carrier is a pharmaceuticallyacceptable carrier. The carrier(s) are “acceptable” in the sense ofbeing compatible with the other ingredients of the formulation and, inthe case of a pharmaceutically acceptable carrier, not deleterious tothe recipient thereof in an amount used in the medicament.

Pharmaceutically acceptable carriers, adjuvants and vehicles that may beused in the pharmaceutical compositions of this invention include, butare not limited to, ion exchangers, alumina, aluminum stearate,lecithin, serum proteins, such as human serum albumin, buffer substancessuch as phosphates, glycine, sorbic acid, potassium sorbate, partialglyceride mixtures of saturated vegetable fatty acids, water, salts orelectrolytes, such as protamine sulfate, disodium hydrogen phosphate,potassium hydrogen phosphate, sodium chloride, zinc salts, colloidalsilica, magnesium trisilicate, polyvinyl pyrrolidone, cellulose-basedsubstances, polyethylene glycol, sodium carboxymethylcellulose,polyacrylates, waxes, polyethylene-polyoxypropylene-block polymers,polyethylene glycol and wool fat.

If required, the solubility and bioavailability of the compounds of thepresent invention in pharmaceutical compositions may be enhanced bymethods well-known in the art. One method includes the use of lipidexcipients in the formulation. See “Oral Lipid-Based Formulations:Enhancing the Bioavailability of Poorly Water-Soluble Drugs (Drugs andthe Pharmaceutical Sciences),” David J. Hauss, ed. Informa Healthcare,2007; and “Role of Lipid Excipients in Modifying Oral and ParenteralDrug Delivery: Basic Principles and Biological Examples,” Kishor M.Wasan, ed. Wiley-Interscience, 2006.

Another known method of enhancing bioavailability is the use of anamorphous form of a compound of this invention optionally formulatedwith a poloxamer, such as LUTROL™ and PLURONIC™ (BASF Corporation), orblock copolymers of ethylene oxide and propylene oxide. See U.S. Pat.No. 7,014,866; and United States patent publications 20060094744 and20060079502.

The pharmaceutical compositions of the invention include those suitablefor oral, rectal, nasal, topical (including buccal and sublingual),vaginal or parenteral (including subcutaneous, intramuscular,intravenous and intradermal) administration. In certain embodiments, thecompound of the formulae herein is administered transdermally (e.g.,using a transdermal patch or iontophoretic techniques). Otherformulations may conveniently be presented in unit dosage form, e.g.,tablets, sustained release capsules, and in liposomes, and may beprepared by any methods well known in the art of pharmacy. See, forexample, Remington's Pharmaceutical Sciences, Mack Publishing Company,Philadelphia, Pa. (17th ed. 1985).

Such preparative methods include the step of bringing into associationwith the molecule to be administered ingredients such as the carrierthat constitutes one or more accessory ingredients. In general, thecompositions are prepared by uniformly and intimately bringing intoassociation the active ingredients with liquid carriers, liposomes orfinely divided solid carriers, or both, and then, if necessary, shapingthe product.

In certain embodiments, the compound is administered orally.Compositions of the present invention suitable for oral administrationmay be presented as discrete units such as capsules, sachets, or tabletseach containing a predetermined amount of the active ingredient; apowder or granules; a solution or a suspension in an aqueous liquid or anon-aqueous liquid; an oil-in-water liquid emulsion; a water-in-oilliquid emulsion; packed in liposomes; or as a bolus, etc. Soft gelatincapsules can be useful for containing such suspensions, which maybeneficially increase the rate of compound absorption.

In the case of tablets for oral use, carriers that are commonly usedinclude lactose and corn starch. Lubricating agents, such as magnesiumstearate, are also typically added. For oral administration in a capsuleform, useful diluents include lactose and dried cornstarch. When aqueoussuspensions are administered orally, the active ingredient is combinedwith emulsifying and suspending agents. If desired, certain sweeteningand/or flavoring and/or coloring agents may be added.

Compositions suitable for oral administration include lozengescomprising the ingredients in a flavored basis, usually sucrose andacacia or tragacanth; and pastilles comprising the active ingredient inan inert basis such as gelatin and glycerin, or sucrose and acacia.

Compositions suitable for parenteral administration include aqueous andnon-aqueous sterile injection solutions which may contain anti-oxidants,buffers, bacteriostats and solutes which render the formulation isotonicwith the blood of the intended recipient; and aqueous and non-aqueoussterile suspensions which may include suspending agents and thickeningagents. The formulations may be presented in unit-dose or multi-dosecontainers, for example, sealed ampules and vials, and may be stored ina freeze dried (lyophilized) condition requiring only the addition ofthe sterile liquid carrier, for example water for injections,immediately prior to use. Extemporaneous injection solutions andsuspensions may be prepared from sterile powders, granules and tablets.

Such injection solutions may be in the form, for example, of a sterileinjectable aqueous or oleaginous suspension. This suspension may beformulated according to techniques known in the art using suitabledispersing or wetting agents (such as, for example, Tween 80) andsuspending agents. The sterile injectable preparation may also be asterile injectable solution or suspension in a non-toxicparenterally-acceptable diluent or solvent, for example, as a solutionin 1,3-butanediol. Among the acceptable vehicles and solvents that maybe employed are mannitol, water, Ringer's solution and isotonic sodiumchloride solution. In addition, sterile, fixed oils are conventionallyemployed as a solvent or suspending medium. For this purpose, any blandfixed oil may be employed including synthetic mono- or diglycerides.Fatty acids, such as oleic acid and its glyceride derivatives are usefulin the preparation of injectables, as are naturalpharmaceutically-acceptable oils, such as olive oil or castor oil,especially in their polyoxyethylated versions. These oil solutions orsuspensions may also contain a long-chain alcohol diluent or dispersant.

The pharmaceutical compositions of this invention may be administered inthe form of suppositories for rectal administration. These compositionscan be prepared by mixing a compound of this invention with a suitablenon-irritating excipient which is solid at room temperature but liquidat the rectal temperature and therefore will melt in the rectum torelease the active components. Such materials include, but are notlimited to, cocoa butter, beeswax and polyethylene glycols.

The pharmaceutical compositions of this invention may be administered bynasal aerosol or inhalation. Such compositions are prepared according totechniques well-known in the art of pharmaceutical formulation and maybe prepared as solutions in saline, employing benzyl alcohol or othersuitable preservatives, absorption promoters to enhance bioavailability,fluorocarbons, and/or other solubilizing or dispersing agents known inthe art. See, e.g.: Rabinowitz, J D and Zaffaroni, A C, U.S. Pat. No.6,803,031, assigned to Alexza Molecular Delivery Corporation.

Topical administration of the pharmaceutical compositions of thisinvention is especially useful when the desired treatment involves areasor organs readily accessible by topical application. For topicalapplication topically to the skin, the pharmaceutical composition shouldbe formulated with a suitable ointment containing the active componentssuspended or dissolved in a carrier. Carriers for topical administrationof the compounds of this invention include, but are not limited to,mineral oil, liquid petroleum, white petroleum, propylene glycol,polyoxyethylene polyoxypropylene compound, emulsifying wax, and water.Alternatively, the pharmaceutical composition can be formulated with asuitable lotion or cream containing the active compound suspended ordissolved in a carrier. Suitable carriers include, but are not limitedto, mineral oil, sorbitan monostearate, polysorbate 60, cetyl esterswax, cetearyl alcohol, 2-octyldodecanol, benzyl alcohol, and water. Thepharmaceutical compositions of this invention may also be topicallyapplied to the lower intestinal tract by rectal suppository formulationor in a suitable enema formulation. Topically-transdermal patches andiontophoretic administration are also included in this invention.

Application of the subject therapeutics may be local, so as to beadministered at the site of interest. Various techniques can be used forproviding the subject compositions at the site of interest, such asinjection, use of catheters, trocars, projectiles, pluronic gel, stents,sustained drug release polymers or other device which provides forinternal access.

Thus, according to yet another embodiment, the compounds of thisinvention may be incorporated into compositions for coating animplantable medical device, such as prostheses, artificial valves,vascular grafts, stents, or catheters. Suitable coatings and the generalpreparation of coated implantable devices are known in the art and areexemplified in U.S. Pat. Nos. 6,099,562; 5,886,026; and 5,304,121. Thecoatings are typically biocompatible polymeric materials such as ahydrogel polymer, polymethyldisiloxane, polycaprolactone, polyethyleneglycol, polylactic acid, ethylene vinyl acetate, and mixtures thereof.The coatings may optionally be further covered by a suitable topcoat offluorosilicone, polysaccharides, polyethylene glycol, phospholipids orcombinations thereof to impart controlled release characteristics in thecomposition. Coatings for invasive devices are to be included within thedefinition of pharmaceutically acceptable carrier, adjuvant or vehicle,as those terms are used herein.

According to another embodiment, the invention provides a method ofcoating an implantable medical device comprising the step of contactingsaid device with the coating composition described above. It will beobvious to those skilled in the art that the coating of the device willoccur prior to implantation into a mammal.

According to another embodiment, the invention provides a method ofimpregnating an implantable drug release device comprising the step ofcontacting said drug release device with a compound or composition ofthis invention. Implantable drug release devices include, but are notlimited to, biodegradable polymer capsules or bullets, non-degradable,diffusible polymer capsules and biodegradable polymer wafers.

According to another embodiment, the invention provides an implantablemedical device coated with a compound or a composition comprising acompound of this invention, such that said compound is therapeuticallyactive.

According to another embodiment, the invention provides an implantabledrug release device impregnated with or containing a compound or acomposition comprising a compound of this invention, such that saidcompound is released from said device and is therapeutically active.

Where an organ or tissue is accessible because of removal from thepatient, such organ or tissue may be bathed in a medium containing acomposition of this invention, a composition of this invention may bepainted onto the organ, or a composition of this invention may beapplied in any other convenient way.

In another embodiment, a composition of this invention further comprisesa second therapeutic agent. The second therapeutic agent may be selectedfrom any compound or therapeutic agent known to have or thatdemonstrates advantageous properties when administered with a compoundhaving the same mechanism of action as pentoxifylline. Such agentsinclude those indicated as being useful in combination withpentoxifylline, including but not limited to, those described in WO1997019686, EP 0640342, WO 2003013568, WO 2001032156, WO 2006035418, andWO 1996005838.

Preferably, the second therapeutic agent is an agent useful in thetreatment or prevention of a disease or condition selected fromperipheral obstructive vascular disease; glomerulonephritis; nephroticsyndrome; nonalcoholic steatohepatitis; Leishmaniasis; cirrhosis; liverfailure; Duchenne's muscular dystrophy; late radiation induced injuries;radiation induced lymphedema; radiation-associated necrosis; alcoholichepatitis; radiation-associated fibrosis; necrotizing enterocolitis inpremature neonates; diabetic nephropathy, hypertension-induced renalfailure, and other chronic kidney disease; Focal SegmentalGlomerulosclerosis; pulmonary sarcoidosis; recurrent aphthousstomatitis; chronic breast pain in breast cancer patients; brain andcentral nervous system tumors; malnutrition-inflammation-cachexiasyndrome; interleukin-1 mediated disease; graft versus host reaction andother allograft reactions; diet-induced fatty liver conditions,atheromatous lesions, fatty liver degeneration and other diet-inducedhigh fat or alcohol-induced tissue-degenerative conditions; humanimmunodeficiency virus type 1 (HIV-1) and other human retroviralinfections; multiple sclerosis; cancer; fibroproliferative diseases;fungal infection; drug-induced nephrotoxicity; collagenous colitis andother diseases and/or conditions characterized by elevated levels ofplatelet derived growth factor (PDGF) or other inflammatory cytokines;endometriosis; optic neuropathy and CNS impairments associated withacquired immunodeficiency syndrome (AIDS), immune disorder diseases, ormultiple sclerosis; autoimmune disease; upper respiratory viralinfection; depression; urinary incontinence; irritable bowel syndrome;septic shock; Alzheimers Dementia; neuropathic pain; dysuria; retinal oroptic nerve damage; peptic ulcer; insulin-dependent diabetes;non-insulin-dependent diabetes; diabetic nephropathy; metabolicsyndrome; obesity; insulin resistance; dyslipidemia; pathologicalglucose tolerance; hypertension; hyperlipidemia; hyperuricemia; gout;hypercoagulability; and inflammation or injury associated withneutrophil chemotaxis and/or degranulation. The compounds of thisinvention can also be used to control intraocular pressure or tostabilize auto-regulation of cerebral blood flow in subjects who requiresuch control as determined by medical examination.

In one embodiment, the second therapeutic agent is selected fromα-tocopherol and hydroxyurea.

In another embodiment, the second therapeutic agent is useful in thetreatment of diabetes or an associated disorder, and is selected frominsulin or insulin analogues, glucagon-like-peptide-1 (GLP-1) receptoragonists, sulfonylurea agents, biguanide agents, alpha-glucosidaseinhibitors, PPAR agonists, meglitinide agents, dipeptidyl-peptidase(DPP) IV inhibitors, other phosphodiesterase (PDE1, PDE5, PDE9, PDE10 orPDE1) inhibitors, amylin agonists, CoEnzyme A inhibitors, andantiobesity agents.

Specific examples of insulin include, but are not limited to Humulin®(human insulin, rDNA origin), Novolin® (human insulin, rDNA origin),Velosulin® BR (human buffered regular insulin, rDNA origin), Exubera®(human insulin, inhaled), and other forms of inhaled insulin, forinstance, as delivered by Mannkind's “Technosphere Insulin System”.

Specific examples of insulin analogues include, but are not limited to,novarapid, insulin detemir, insulin lispro, insulin glargine, insulinzinc suspension and Lys-Pro insulin.

Specific examples of Glucagon-Like-Peptide-1 receptor agonists include,but are not limited to BIM-51077 (CAS-No. 275371-94-3), EXENATIDE(CAS-No. 141758-74-9), CJC-1131 (CAS-No. 532951-64-7), LIRAGLUTIDE(CAS-No. 20656-20-2) and ZP-10 (CAS-No. 320367-13-3).

Specific examples of sulfonylurea agents include, but are not limitedto, TOLBUTAMIDE (CAS-No. 000064-77-7), TOLAZAMIDE (CAS-No. 001156-19-0),GLIPIZIDE (CAS-No. 029094-61-9), CARBUTAMIDE (CAS-No. 000339-43-5),GLISOXEPIDE (CAS-No. 025046-79-1), GLISENTIDE (CAS-No. 032797-92-5),GLIBORNURIDE (CAS-No. 026944-48-9), GLIBENCLAMIDE (CAS-NO. 010238-21-8),GLIQUIDONE (CAS-No. 033342-05-1), GLIMEPIRIDE (CAS-No. 093479-97-1) andGLICLAZIDE (CAS-No. 021187-98-4).

A specific example of a biguanide agent includes, but is not limited toMETFORMIN (CAS-No. 000657-24-9).

Specific examples of alpha-glucosidase-inhibitors include, but are notlimited to ACARBOSE (Cas-No. 056180-94-0), MIGLITOL (CAS-No.072432-03-2) and VOGLIBOSE (CAS-No. 083480-29-9).

Specific examples of PPAR-agonists include, but are not limited toMURAGLITAZAR (CAS-No. 331741-94-7), ROSIGLITAZONE (CAS-NO. 122320-73-4),PIOGLITAZONE (CAS-No. 111025-46-8), RAGAGLITAZAR (CAS-NO. 222834-30-2),FARGLITAZAR (CAS-No. 196808-45-4), TESAGLITAZAR (CAS-No. 251565-85-2),NAVEGLITAZAR (CAS-No. 476436-68-7), NETOGLITAZONE (CAS-NO. 161600-01-7),RIVOGLITAZONE (CAS-NO. 185428-18-6), K-1 11 (CAS-No. 221564-97-2),GW-677954 (CAS-No. 622402-24-8), FK-614 (CAS-No 193012-35-0) and(−)-Halofenate (CAS-No. 024136-23-0). Preferred PPAR-agonists areROSGLITAZONE and PIOGLITAZONE.

Specific examples of meglitinide agents include, but are not limited toREPAGLINIDE (CAS-No. 135062-02-1), NATEGLINIDE (CAS-No. 105816-04-4) andMITIGLINIDE (CAS-No. 145375-43-5).

Specific examples of DPP IV inhibitors include, but are not limited toSITAGLIPTIN (CAS-No. 486460-32-6), SAXAGLIPTIN (CAS-No. 361442-04-8),VILDAGLIPTIN (CAS-No. 274901-16-5), DENAGLIPTIN (CAS-No. 483369-58-0),P32/98 (CAS-No. 251572-70-0) and NVP-DPP-728 (CAS-No. 247016-69-9).

Specific examples of PDE5 inhibitors include, but are not limited toSILDENAFIL (CAS-No. 139755-83-2), VARDENAFIL (CAS-No. 224785-90-4) andTADALAFIL (CAS-No. 171596-29-5). Examples of PDE1, PDE9, PDE10 or PDE11inhibitors which may be usefully employed according to the presentinvention can be found, for example, in US20020160939, WO2003037432,US2004220186, WO2005/003129, WO2005012485, WO2005120514 and WO03077949.

A specific example of an amylin agonist includes, but is not limited toPRAMLINITIDE (CAS-No. 151126-32-8).

A specific example of a Coenzyme A inhibitor includes, but is notlimited to ETOMOXIR (CAS-No. 082258-36-4).

Specific examples of anti-obesity drugs include, but are not limited toHMR-1426 (CAS-No. 262376-75-0), CETILISTAT (CAS-No. 282526-98-1) andSIBUTRAMINE (CAS-No. 106650-56-0).

In another embodiment, the invention provides separate dosage forms of acompound of this invention and one or more of any of the above-describedsecond therapeutic agents, wherein the compound and second therapeuticagent are associated with one another. The term “associated with oneanother” as used herein means that the separate dosage forms arepackaged together or otherwise attached to one another such that it isreadily apparent that the separate dosage forms are intended to be soldand administered together (within less than 24 hours of one another,consecutively or simultaneously).

In the pharmaceutical compositions of the invention, the compound of thepresent invention is present in an effective amount. As used herein, theterm “effective amount” refers to an amount which, when administered ina proper dosing regimen, is sufficient to treat (therapeutically orprophylactically) the target disorder. For example, and effective amountis sufficient to reduce or ameliorate the severity, duration orprogression of the disorder being treated, prevent the advancement ofthe disorder being treated, cause the regression of the disorder beingtreated, or enhance or improve the prophylactic or therapeutic effect(s)of another therapy.

The interrelationship of dosages for animals and humans (based onmilligrams per meter squared of body surface) is described in Freireichet al., Cancer Chemother. Rep, 1966, 50: 219. Body surface area may bedetermined approximately from height and weight of the patient. See,e.g., Scientific Tables, Geigy Pharmaceuticals, Ardsley, N.Y., 1970,537.

In one embodiment, an effective amount of a compound of this inventionis in the range of 20 mg to 2000 mg per treatment. In more specificembodiments the amount is in the range of 40 mg to 1000 mg, or in therange of 100 mg to 800 mg, or more specifically in the range of 200 mgto 400 mg per treatment. Treatment typically is administered from one tothree times daily.

Effective doses will also vary, as recognized by those skilled in theart, depending on the diseases treated, the severity of the disease, theroute of administration, the sex, age and general health condition ofthe patient, excipient usage, the possibility of co-usage with othertherapeutic treatments such as use of other agents and the judgment ofthe treating physician. For example, guidance for selecting an effectivedose can be determined by reference to the prescribing information forpentoxifylline.

For pharmaceutical compositions that comprise a second therapeuticagent, an effective amount of the second therapeutic agent is betweenabout 20% and 100% of the dosage normally utilized in a monotherapyregime using just that agent. Preferably, an effective amount is betweenabout 70% and 100% of the normal monotherapeutic dose. The normalmonotherapeutic dosages of these second therapeutic agents are wellknown in the art. See, e.g., Wells et al., eds., PharmacotherapyHandbook, 2nd Edition, Appleton and Lange, Stamford, Conn. (2000); PDRPharmacopoeia, Tarascon Pocket Pharmacopoeia 2000, Deluxe Edition,Tarascon Publishing, Loma Linda, Calif. (2000), each of which referencesare incorporated herein by reference in their entirety.

It is expected that some of the second therapeutic agents referencedabove will act synergistically with the compounds of this invention.When this occurs, it will allow the effective dosage of the secondtherapeutic agent and/or the compound of this invention to be reducedfrom that required in a monotherapy. This has the advantage ofminimizing toxic side effects of either the second therapeutic agent ofa compound of this invention, synergistic improvements in efficacy,improved ease of administration or use and/or reduced overall expense ofcompound preparation or formulation.

Methods of Treatment

In one embodiment, the invention provides a method of inhibiting theactivity of phosphodiesterase (PDE) in a cell, comprising contacting acell with one or more compounds of Formula A, A1, I, II or B.

In addition to its PDE inhibitory activity, pentoxifylline is known tosuppress the production of a number of other biological agents such asinterleukin-1 (IL-1), IL-6, IL-12, TNF-alpha, fibrinogen, and variousgrowth factors. Accordingly, in another embodiment, the inventionprovides a method of suppressing the production of interleukin-1 (IL-1),IL-6, IL-12, TNF-alpha, fibrinogen, and various growth factors in acell, comprising contacting a cell with one or more compounds of FormulaA, A1, I, II or B.

According to another embodiment, the invention provides a method oftreating a disease in a patient in need thereof that is beneficiallytreated by pentoxifylline comprising the step of administering to saidpatient an effective amount of a compound of Formula A, A1, I, II or Bor a pharmaceutical composition comprising a compound of Formula A, A1,I, II or B and a pharmaceutically acceptable carrier.

Such diseases are well known in the art and are disclosed in, but notlimited to the following patents and published applications: WO1988004928, EP 0493682, U.S. Pat. No. 5,112,827, EP 0484785, WO1997019686, WO 2003013568, WO 2001032156, WO 1992007566, WO 1998055110,WO 2005023193, U.S. Pat. No. 4,975,432, WO 1993018770, EP 0490181, andWO 1996005836. Such diseases include, but are not limited to, peripheralobstructive vascular disease; glomerulonephritis; nephrotic syndrome;nonalcoholic steatohepatitis; Leishmaniasis; cirrhosis; liver failure;Duchenne's muscular dystrophy; late radiation induced injuries;radiation induced lymphedema; radiation-associated necrosis; alcoholichepatitis; radiation-associated fibrosis; necrotizing enterocolitis inpremature neonates; diabetic nephropathy, hypertension-induced renalfailure, and other chronic kidney disease; Focal SegmentalGlomerulosclerosis; pulmonary sarcoidosis; recurrent aphthousstomatitis; chronic breast pain in breast cancer patients; brain andcentral nervous system tumors; malnutrition-inflammation-cachexiasyndrome; interleukin-1 mediated disease; graft versus host reaction andother allograft reactions; diet-induced fatty liver conditions,atheromatous lesions, fatty liver degeneration and other diet-inducedhigh fat or alcohol-induced tissue-degenerative conditions; humanimmunodeficiency virus type 1 (HIV-1) and other human retroviralinfections; multiple sclerosis; cancer; fibroproliferative diseases;fungal infection; drug-induced nephrotoxicity; collagenous colitis andother diseases and/or conditions characterized by elevated levels ofplatelet derived growth factor (PDGF) or other inflammatory cytokines;endometriosis; optic neuropathy and CNS impairments associated withacquired immunodeficiency syndrome (AIDS), immune disorder diseases, ormultiple sclerosis; autoimmune disease; upper respiratory viralinfection; depression; urinary incontinence; irritable bowel syndrome;septic shock; Alzheimers Dementia; neuropathic pain; dysuria; retinal oroptic nerve damage; peptic ulcer; insulin-dependent diabetes;non-insulin-dependent diabetes; diabetic nephropathy; metabolicsyndrome; obesity; insulin resistance; dyslipidemia; pathologicalglucose tolerance; hypertension; hyperlipidemia; hyperuricemia; gout;hypercoagulability; acute alcoholic hepatitis; olfaction disorders;patent ductus arteriosus; and inflammation or injury associated withneutrophil chemotaxis and/or degranulation.

The compounds of Formula A, A1, I, II or B can also be used to controlintraocular pressure or to stabilize auto-regulation of cerebral bloodflow in subjects who require such control as determined by medicalexamination.

In one particular embodiment, the method of this invention is used totreat a disease or condition in a patient in need thereof selected fromintermittent claudication on the basis of chronic occlusive arterialdisease of the limbs and other peripheral obstructive vascular diseases;glomerulonephritis; Focal Segmental Glomerulosclerosis; nephroticsyndrome; nonalcoholic steatohepatitis; Leishmaniasis; cirrhosis; liverfailure; Duchenne's muscular dystrophy; late radiation induced injuries;radiation induced lymphedema; alcoholic hepatitis; radiation-inducedfibrosis; necrotizing enterocolitis in premature neonates; diabeticnephropathy, hypertension-induced renal failure and other chronic kidneydiseases; pulmonary sarcoidosis; recurrent aphthous stomatitis; chronicbreast pain in breast cancer patients; brain and central nervous systemtumors; obesity; acute alcoholic hepatitis; olfaction disorders;endometriosis-associated infertility; malnutrition-inflammation-cachexiasyndrome; and patent ductus arteriosus.

In one embodiment, the method of this invention is used to treatdiabetic nephropathy, hypertensive nephropathy or intermittentclaudication on the basis of chronic occlusive arterial disease of thelimbs. In another particular embodiment, the method of this invention isused to treat a disease or condition in a patient in need thereofselected from intermittent claudication on the basis of chronicocclusive arterial disease of the limbs.

In one embodiment, the method of this invention is used to treat chronickidney disease. The chronic kidney disease may be selected fromglomerulonephritis, focal segmental glomerulosclerosis, nephroticsyndrome, reflux uropathy, or polycystic kidney disease.

In one embodiment, the method of this invention is used to treat chronicdisease of the liver. The chronic disease of the liver may be selectedfrom nonalcoholic steatohepatitis, fatty liver degeneration or otherdiet-induced high fat or alcohol-induced tissue-degenerative conditions,cirrhosis, liver failure, or alcoholic hepatitis.

In one embodiment, the method of this invention is used to adiabetes-related disease or condition. This disease may be selected frominsulin resistance, retinopathy, diabetic ulcers, radiation-associatednecrosis, acute kidney failure or drug-induced nephrotoxicity.

In one embodiment, the method of this invention is used to treat apatient suffering from cystic fibrosis, including those patientssuffering from chronic Pseudomonas bronchitis.

In one embodiment, the method of this invention is used to aid in woundhealing. Examples of types of wounds that may be treated include venousulcers, diabetic ulcers and pressure ulcers.

In another particular embodiment, the method of this invention is usedto treat a disease or condition in a patient in need thereof selectedfrom insulin dependent diabetes; non-insulin dependent diabetes;metabolic syndrome; obesity; insulin resistance; dyslipidemia;pathological glucose tolerance; hypertension; hyperlipidemia;hyperuricemia; gout; and hypercoagulability.

Methods delineated herein also include those wherein the patient isidentified as in need of a particular stated treatment. Identifying apatient in need of such treatment can be in the judgment of a patient ora health care professional and can be subjective (e.g. opinion) orobjective (e.g. measurable by a test or diagnostic method).

In another embodiment, any of the above methods of treatment comprisesthe further step of co-administering to the patient one or more secondtherapeutic agents. The choice of second therapeutic agent may be madefrom any second therapeutic agent known to be useful forco-administration with pentoxifylline. The choice of second therapeuticagent is also dependent upon the particular disease or condition to betreated. Examples of second therapeutic agents that may be employed inthe methods of this invention are those set forth above for use incombination compositions comprising a compound of this invention and asecond therapeutic agent.

In particular, the combination therapies of this invention includeco-administering a compound of Formula A, A1, I, II or B and a secondtherapeutic agent for treatment of the following conditions (with theparticular second therapeutic agent indicated in parentheses followingthe indication): late radiation induced injuries (α-tocopherol),radiation-induced fibrosis (α-tocopherol), radiation induced lymphedema(α-tocopherol), chronic breast pain in breast cancer patients(α-tocopherol), type 2 diabetic nephropathy (captopril),malnutrition-inflammation-cachexia syndrome (oral nutritionalsupplement, such as Nepro; and oral anti-inflammatory module, such asOxepa); and brain and central nervous system tumors (radiation therapyand hydroxyurea).

The combination therapies of this invention also includeco-administering a compound of Formula A, A1, I, II or B and a secondtherapeutic agent for treatment of insulin dependent diabetes;non-insulin dependent diabetes; metabolic syndrome; obesity; insulinresistance; dyslipidemia; pathological glucose tolerance; hypertension;hyperlipidemia; hyperuricemia; gout; and hypercoagulability.

The term “co-administered” as used herein means that the secondtherapeutic agent may be administered together with a compound of thisinvention as part of a single dosage form (such as a composition of thisinvention comprising a compound of the invention and an secondtherapeutic agent as described above) or as separate, multiple dosageforms. Alternatively, the additional agent may be administered prior to,consecutively with, or following the administration of a compound ofthis invention. In such combination therapy treatment, both thecompounds of this invention and the second therapeutic agent(s) areadministered by conventional methods. The administration of acomposition of this invention, comprising both a compound of theinvention and a second therapeutic agent, to a patient does not precludethe separate administration of that same therapeutic agent, any othersecond therapeutic agent or any compound of this invention to saidpatient at another time during a course of treatment.

Effective amounts of these second therapeutic agents are well known tothose skilled in the art and guidance for dosing may be found in patentsand published patent applications referenced herein, as well as in Wellset al., eds., Pharmacotherapy Handbook, 2nd Edition, Appleton and Lange,Stamford, Conn. (2000); PDR Pharmacopoeia, Tarascon Pocket Pharmacopoeia2000, Deluxe Edition, Tarascon Publishing, Loma Linda, Calif. (2000),and other medical texts. However, it is well within the skilledartisan's purview to determine the second therapeutic agent's optimaleffective-amount range.

In one embodiment of the invention, where a second therapeutic agent isadministered to a subject, the effective amount of the compound of thisinvention is less than its effective amount would be where the secondtherapeutic agent is not administered. In another embodiment, theeffective amount of the second therapeutic agent is less than itseffective amount would be where the compound of this invention is notadministered. In this way, undesired side effects associated with highdoses of either agent may be minimized. Other potential advantages(including without limitation improved dosing regimens and/or reduceddrug cost) will be apparent to those of skill in the art.

In yet another aspect, the invention provides the use of a compound ofFormula A, A1, I, II or B alone or together with one or more of theabove-described second therapeutic agents in the manufacture of amedicament, either as a single composition or as separate dosage forms,for treatment or prevention in a patient of a disease, disorder orsymptom set forth above. Another aspect of the invention is a compoundof Formula A, A1, I, II or B for use in the treatment or prevention in apatient of a disease, disorder or symptom thereof delineated herein.

Diagnostic Methods and Kits

The present invention also provides kits for use to treat peripheralobstructive vascular disease, in particular intermittent claudication onthe basis of chronic occlusive arterial disease of the limbs;glomerulonephritis; nephrotic syndrome; nonalcoholic steatohepatitis;Leishmaniasis; cirrhosis; liver failure; Duchenne's muscular dystrophy;late radiation induced injuries; radiation induced lymphedema; alcoholichepatitis; radiation fibrosis; necrotizing enterocolitis in prematureneonates; chronic kidney disease; pulmonary sarcoidosis; recurrentaphthous stomatitis; chronic breast pain in breast cancer patients;brain and central nervous system tumors;malnutrition-inflammation-cachexia syndrome; insulin dependent diabetes;non-insulin dependent diabetes; metabolic syndrome; obesity; insulinresistance; dyslipidemia; pathological glucose tolerance; hypertension;hyperlipidemia; hyperuricemia; gout; and hypercoagulability. These kitscomprise (a) a pharmaceutical composition comprising a compound ofFormula A, A1, I, II or B or a salt thereof, wherein said pharmaceuticalcomposition is in a container; and (b) instructions describing a methodof using the pharmaceutical composition to treat peripheral obstructivevascular disease, in particular intermittent claudication on the basisof chronic occlusive arterial disease of the limbs; glomerulonephritis;nephrotic syndrome; nonalcoholic steatohepatitis; Leishmaniasis;cirrhosis; liver failure; Duchenne's muscular dystrophy; late radiationinduced injuries; radiation induced lymphedema; alcoholic hepatitis;radiation fibrosis; necrotizing enterocolitis in premature neonates;chronic kidney disease; pulmonary sarcoidosis; recurrent aphthousstomatitis; chronic breast pain in breast cancer patients; brain andcentral nervous system tumors; malnutrition-inflammation-cachexiasyndrome; insulin dependent diabetes; non-insulin dependent diabetes;metabolic syndrome; obesity; insulin resistance; dyslipidemia;pathological glucose tolerance; hypertension; hyperlipidemia;hyperuricemia; gout; and hypercoagulability.

The container may be any vessel or other sealed or sealable apparatusthat can hold said pharmaceutical composition. Examples include bottles,ampules, divided or multi-chambered holders bottles, wherein eachdivision or chamber comprises a single dose of said composition, adivided foil packet wherein each division comprises a single dose ofsaid composition, or a dispenser that dispenses single doses of saidcomposition. The container can be in any conventional shape or form asknown in the art which is made of a pharmaceutically acceptablematerial, for example a paper or cardboard box, a glass or plasticbottle or jar, a re-sealable bag (for example, to hold a “refill” oftablets for placement into a different container), or a blister packwith individual doses for pressing out of the pack according to atherapeutic schedule. The container employed can depend on the exactdosage form involved, for example a conventional cardboard box would notgenerally be used to hold a liquid suspension. It is feasible that morethan one container can be used together in a single package to market asingle dosage form. For example, tablets may be contained in a bottle,which is in turn contained within a box. In one embodiment, thecontainer is a blister pack.

The kits of this invention may also comprise a device to administer orto measure out a unit dose of the pharmaceutical composition. Suchdevice may include an inhaler if said composition is an inhalablecomposition; a syringe and needle if said composition is an injectablecomposition; a syringe, spoon, pump, or a vessel with or without volumemarkings if said composition is an oral liquid composition; or any othermeasuring or delivery device appropriate to the dosage formulation ofthe composition present in the kit.

In certain embodiment, the kits of this invention may comprise in aseparate vessel of container a pharmaceutical composition comprising asecond therapeutic agent, such as one of those listed above for use forco-administration with a compound of this invention.

SYNTHETIC EXAMPLES

The synthetic examples below provide detailed procedures for makingcertain compounds of this invention. It will be apparent to one skilledin the art that further compounds of this invention may be preparedthrough the use of other reagents or intermediates by reference to theseprocedures and the schemes described above. The prepared compounds wereanalyzed by NMR, mass spectrometry, and/or elemental analysis asindicated. ¹HNMR were taken on a 300 MHz instrument, which was usefulfor determining deuterium incorporation. Unless otherwise stated, theabsence of an NMR signal as noted in the examples below indicates alevel of deuterium incorporation that is at least 90%.

Example 1 Synthesis of3-Methyl-7-(methyl-d₃)-1-(5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 100)

Step 1. 3-Methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione (51)

A suspension of 3-methylxanthine 50 (5.0 g, 30.1 mmol, 1 equiv) andpowdered K₂CO₃ (5.0 g, 36.0 mmol, 1.2 equiv) in DMF (95 mL) was heatedto 60° C. and iodomethane-d₃ (Cambridge Isotopes, 99.5 atom % D, 2.2 mL,36.0 mmol, 1.2 equiv) was added via syringe. The resulting mixture washeated at 80° C. for 5 hours (h). The reaction mixture was cooled toroom temperature (rt) and the DMF was evaporated under reduced pressure.The crude residue was dissolved in 5% aqueous NaOH (50 mL), resulting ina dull yellow solution. The aqueous solution was washed with DCM threetimes (500 mL total). The aqueous layer was acidified to pH 5 withacetic acid (6 mL), resulting in formation of a tan precipitate. Themixture was cooled in an ice-water bath, and the solids were filteredand washed with cold water. The solid was dried in a vacuum oven to give2.9 g of 51 as a tan solid. The filtrate was concentrated toapproximately 25 mL and a second crop (0.70 g) of 51 was collected byfiltration. The total yield of 51 was 3.6 g. The crude material was usedwithout further purification.

Step 2. 3-Methyl-7-(methyl-d₃)-1-(5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 100)

Crude 51 (1.50 g, 8.2 mmol, 1 equiv) and powdered K₂CO₃ (2.28 g, 16.4mmol, 2 equiv) were suspended in DMF (30 mL) and heated to 50° C. To theresulting tan suspension was added 6-chloro-2-hexanone (52, 1.2 mL, 9.0mmol, 1.1 equiv) and the reaction temperature was raised to 130° C.Heating was continued at 130° C. for 2 h, during which time thesuspension became finer and darker in color. The reaction mixture wascooled to rt and DMF was evaporated under reduced pressure. The residualtan paste was suspended in EtOAc (250 mL) and filtered to removeinsoluble material. The filtrate was concentrated under reduced pressureresulting in a yellow oil. The crude product was purified using anAnalogix chromatography system eluting with 100% EtOAc (10 minutes)followed by a gradient of 0 to 25% MeOH/EtOAc over 50 minutes (min).Product fractions were concentrated under reduced pressure to give aslightly yellow oil that solidified after standing for several minutes.The solid was triturated with heptanes (100 mL) and filtered to give2.00 g of 100 as an off-white solid, mp 101.8-103.0° C. ¹H-NMR (300 MHz,CDCl₃): δ 1.64-1.68 (m, 4H), 2.15 (s, 3H), 2.51 (t, J=7.0, 2H), 3.57 (s,3H), 4.01 (t, J=7.0, 2H), 7.52 (s, 1H). ¹³C-NMR (75 MHz, CDCl₃): δ20.95, 27.41, 29.69, 29.98, 40.80, 43.18, 107.63, 141.41, 148.75,151.45, 155.26, 208.80. HPLC (method: 20 mm C18-RP column—gradientmethod 2 to 95% ACN+0.1% formic acid in 3.3 min with 1.7 min hold at 95%ACN; Wavelength: 254 nm): retention time: 2.54 min; 98.5% purity. MS(M+H): 282.0. Elemental Analysis (C₁₃H₁₅D₃N₄O₃): Calculated: C=55.50,H=6.45, N=19.92. Found: C=55.58, H=6.48, N=19.76.

Due to the presence of a triplet at 4.01 ppm in the above ¹H-NMRspectrum, determination of the presence or absence of a singlet peak ataround 3.99 ppm corresponding to the presence or absence of hydrogens onthe N-methyl group at the 7 position (R¹) of the purine ring was notpossible.

Example 2 Synthesis of8-d₁-3-methyl-7-(methyl-d₃)-1-(6-d₃-4-d₂-5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 409)8-d₁-3-methyl-7-(methyl-d₃)-1-(6-d₃-4-d₂-5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 409)

A suspension of 100 (1.80 g, 6.4 mmol, 1 equiv) and powdered K₂CO₃ (0.23g, 1.7 mmol, 0.25 equiv) in D₂O (Cambridge Isotope Labs, 99 atom % D)(45 mL) was stirred under reflux conditions for 24 h during which timethe suspension became a slightly yellow solution. The reaction mixturewas cooled to rt, saturated with sodium chloride, and extracted fourtimes with dichloromethane (400 mL total). The combined organic solutionwas dried over Na₂SO₄, filtered, and evaporated under reduced pressureto provide 1.7 g of a slightly yellow oil that solidified upon standing.The crude material was re-subjected to the hydrogen/deuterium exchangeconditions described above with fresh K₂CO₃ and D₂O. After an identicalworkup, the off-white solid was triturated with hexanes (100 mL) andfiltered to give 1.61 g of 409 as an off white solid, mp 99.6-99.8° C.¹H-NMR (300 MHz, CDCl₃): δ 1.64-1.69 (m, 4H), 3.57 (s, 3H), 4.01 (t,J=7.0, 2H). ¹³C-NMR (75 MHz, CDCl₃): δ 21.05, 27.61, 29.90, 41.02,107.83, 148.99, 151.69, 155.50, 209.28. HPLC (method: Waters Atlantis T32.1×50 mm 3 μm C18-RP column—gradient method 5-95% ACN+0.1% formic acidin 14 min (1.0 mL/min) with 4 min hold at 95% ACN; Wavelength: 254 nm):retention time: 3.26 min; 98% purity. MS (M+H): 288.3. ElementalAnalysis (C₁₃H₉D₉N₄O₃): Calculated: C=54.35, H=6.31, N=19.50. Found:C=54.36, H=6.32, N=19.10.

Notable in the ¹H-NMR spectrum above was the absence of the followingpeaks: a singlet at around 2.15 ppm indicating an absence of methylketone hydrogens; a triplet at around 2.51 ppm indicating an absence ofmethylene ketone hydrogens; and a singlet at around 7.52 ppm indicatingan absence of hydrogen at the number 8 position on the purine ring. Dueto the presence of a triplet at 4.01 ppm in the above ¹H-NMR spectrum,determination of the presence or absence of a singlet peak at around3.99 ppm corresponding to the presence or absence of hydrogens on theN-methyl group at the 7 position (R¹) of the purine ring was notpossible.

Example 3 Synthesis of3,7-Di(methyl-d₃)-1-(5-oxohexyl)-1H-purine-2,6(3H,7H)-dione (Compound101)

Step 1. 3,7-Di(methyl-d₃)-1H-purine-2,6(3H,7H)-dione (55)

A suspension of xanthine 53 (2.00 g, 13.2 mmol, 1.0 equiv) andhexamethyldisilazane (32 mL) in toluene (60 mL) was heated to reflux andstirred for 4 days. The reaction mixture was cooled to room temperature,diluted with additional toluene (50 mL) and filtered through Celite toremove any unreacted starting material. The filtrate was evaporated todryness under reduced pressure to produce 54 as a white solid (4.1 g). Aportion of this material (3.00 g) was placed in a 100 mL sealed tubereaction vessel, followed by the addition of toluene (60 mL) and CD₃I (4mL, Cambridge Isotopes, 99.5 atom % D). The reaction mixture was heatedin a 120° C. oil bath and stirred for 24 hours, during which time thereaction mixture turned yellow and a solid formed. The reaction mixturewas cooled to room temperature, resulting in the entire reaction mixturesolidifying to a yellow solid. The mixture was diluted with acetone (30mL) and MeOH (5 mL) and filtered under a stream of N₂. The solids werewashed with acetone (100 mL) which removed the yellow color to afford anoff-white solid. The solid was dried on the filter under a stream of N₂to give a mixture of 55 and monoalkylated side product,7-(methyl-d₃)-xanthine in a roughly 1:1 ratio. Total mass recovery was2.6 g (42% crude yield). Due to the poor solubility of this mixture, itwas carried forward without further purification.

Step 2. 3,7-Di(methyl-d₃)-1-(5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 101)

A suspension of crude 55 (2.50 g, 13.4 mmol, 1.0 equiv) and powderedK₂CO₃ (2.20 g, 16 mmol, 1.2 equiv) in DMF (50 mL) was heated to 60° C.To the resulting tan suspension was added 6-chloro-2-hexanone 52 (2.0mL, 14.8 mmol, 1.1 equiv) and the mixture was heated to 140° C. Heatingwas continued at 140° C. for 4 hours during which time the suspensionbecame finer and darker in color. The reaction mixture was cooled toroom temperature and the DMF was evaporated under reduced pressure. Theresulting tan paste was suspended in 1:1 dichloromethane/ethyl acetate(200 mL) and filtered to remove insoluble material. The filtrate wasconcentrated under reduced pressure giving a yellowish-brown oil (3.0g). This crude reaction product was adsorbed onto silica gel anddry-loaded onto a silica gel column packed with 100% dichloromethane.The column was eluted with a gradient of 0-5% MeOH/dichloromethane.Fractions containing product were concentrated under reduced pressure togive 0.75 g of a yellow oil. LCMS showed the material to be about 90%pure. The yellow oil was further purified using an Analogixchromatography system eluting initially with 60% EtOAc/heptanes followedby a gradient of 60-100% EtOAc/heptanes over 20 min. The desired producteluted at about 20 minutes. Fractions containing product wereconcentrated under reduced pressure to give 0.55 g (16%) of Compound 101as a slightly yellow oil which solidified upon standing. ¹H-NMR (300MHz, CDCl₃): δ 1.64-1.69 (m, 4H), 2.15 (s, 3H), 2.51 (t, J=7.0, 2H),4.02 (t, J=7.0, 2H), 7.51 (s, 1H). ¹³C-NMR (75 MHz, CDCl₃): δ 20.97,27.43, 29.97, 40.80, 43.19, 107.64, 141.40, 148.78, 151.48, 155.29,208.77. HPLC (method: Waters Atlantis T3 2.1×50 mm 3 μm C18-RPcolumn—gradient method 5-95% ACN+0.1% formic acid in 14 min (1.0 mL/min)with 4 min hold at 95% ACN+0.1% formic acid; Wavelength: 305 nm):retention time: 3.24 min; 98.6% purity. MS (M+H): 285.3, (M+Na): 307.2.Elemental Analysis (C₁₃H₁₂D₆N₄O₃): Calculated: C=54.92, H=6.38, N=19.71.Found: C=54.90, H=6.40, N=19.50.

Notable in the ¹H-NMR spectrum above was the absence of a singlet ataround 3.57 ppm indicating an absence of N-methyl hydrogens at the 3position of the purine ring. Due to the presence of a triplet at 4.01ppm in the above ¹H-NMR spectrum, determination of the presence orabsence of a singlet peak at around 3.99 ppm corresponding to thepresence or absence of hydrogens on the N-methyl group at the 7 position(R¹) of the purine ring was not possible.

Example 4 Synthesis of8-d₁-3,7-Di(methyl-d₃)-1-(4,4,6,6,6-d₅-5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 413)8-d₁-3,7-Di(methyl-d₃)-1-(4-d₂-6-d₃-5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 413)

A suspension of Compound 101 (0.60 g, 2.1 mmol, 1.0 equiv) and powderedK₂CO₃ (0.10 g, 0.72 mmol, 0.30 equiv) in D₂O (15 mL, Cambridge Isotopes,99 atom % D) was heated and stirred at reflux for 16 hours during whichtime the suspension became a slightly yellow solution. The reactionmixture was cooled to room temperature, saturated with sodium chloride,and extracted four times with dichloromethane (200 mL). The combinedorganic extracts were dried over Na₂SO₄, filtered, and concentratedunder reduced pressure to provide 0.53 g of a slightly yellow oil thatsolidified upon standing. The crude reaction product was re-subjected tothe above reaction conditions with fresh powdered K₂CO₃ and D₂O. Afteran identical workup, the off-white solid was triturated with hexanes (50mL) and filtered to give 0.45 g (74%) of Compound 413 as an off-whitesolid, mp 99.2-99.3° C. ¹H-NMR (300 MHz, CDCl₃): δ 1.64-1.71 (m, 4H),4.01 (t, J=7.0, 2H). ¹³C-NMR (75 MHz, CDCl₃): δ 20.85, 27.41, 40.81,107.63, 148.80, 151.50, 155.31, 209.09. HPLC (method: Waters Atlantis T32.1×50 mm 3 μm C18-RP column—gradient method 5-95% ACN+0.1% formic acidin 14 minutes (1.0 mL/min) with a 4 minute hold at 95% ACN+0.1% formicacid; Wavelength: 254 nm): retention time: 3.25 min; 98.7% purity. MS(M+H): 291.3, (M+Na): 313.2. Elemental Analysis (C₁₃H₆D₁₂N₄O₃):Calculated: C=53.78, H=6.25, N=19.30. Found: C=53.76, H=6.39, N=19.11.

Notable in the ¹H-NMR spectrum above was the absence of the followingpeaks: a singlet at around 2.15 ppm indicating an absence of methylketone hydrogens; a triplet at around 2.51 ppm indicating an absence ofmethylene ketone hydrogens; a singlet around 3.57 ppm indicating anabsence of N-methyl hydrogens at the 3 position on the purine ring; anda singlet at around 7.51 ppm indicating an absence of hydrogen at thenumber 8 position on the purine ring. Due to the presence of a tripletat 4.01 ppm in the above ¹H-NMR spectrum, determination of the presenceor absence of a singlet peak at around 3.99 ppm corresponding to thepresence or absence of hydrogens on the N-methyl group at the 7 position(R¹) of the purine ring was not possible.

Example 5 Synthesis of3-Methyl-7-(methyl-d₃)-1-(6,6,6-d₃-5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 99)

Step 1.5-(3-Methyl-7-(methyl-d₃)-2,3,6,7-tetrahydro-1H-purin-1-yl)-N-methoxy-N-methylpentanamide(58)

A suspension of 51 (1.50 g, 8.2 mmol, 1.0 equiv, see Example 1 forpreparation) and powdered K₂CO₃ (1.80 g, 12.9 mmol, 1.6 equiv) in DMF(40 mL) was heated to 60° C. 5-Bromo-N-methoxy-N-methylpentanamide 57(2.21 g, 9.8 mmol, 1.2 equiv, prepared as outlined in Org. Lett., 2005,7: 1427-1429) was added and the mixture was heated at 110° C. for 4hours during which time the suspended solid became finer and tan incolor. The reaction mixture was cooled to room temperature and DMF wasevaporated under reduced pressure. The resulting tan paste was suspendedin 1:1 CH₂Cl₂:ethyl acetate (250 mL) and the suspension was filtered toremove insoluble material. The filtrate was concentrated under reducedpressure to a yellow oil. This crude reaction product was purified usingan Analogix automated chromatography system eluting with 100% CH₂Cl₂ for8 minutes followed by a gradient of 0-5% MeOH/CH₂Cl₂ over 40 minutes.The desired product eluted at approximately 24 minutes. Fractionscontaining product were concentrated under reduced pressure to aslightly yellow oil. ¹H NMR of the oil indicated it containedapproximately 10% unreacted 51. A second purification on an Analogixautomated chromatography system eluting with 100% CH₂Cl₂ for 10 minutesfollowed by a gradient of 0-5% MeOH/CH₂Cl₂ over 50 minutes allowed forremoval of the impurity. Fractions containing product were concentratedunder reduced pressure to a slightly yellow oil that crystallized as anoff-white solid on standing. The solid was triturated with heptanes (100mL) and filtered to give 1.29 g (49%) of 58 as an off-white solid.

Step 2.3-Methyl-7-(methyl-d₃)-1-(6,6,6-d₃-5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 99)

A suspension of 58 (0.72 g, 2.2 mmol, 1.0 equiv) in THF (20 mL) wascooled to 2° C. and 1M CD₃MgI in ether (2.4 mL, 2.4 mmol, 1.1 equiv,Aldrich>99 atom % D) was added drop-wise via syringe at a rate tomaintain the temperature below 5° C. During the addition, the mixturebecame a fine, slightly yellow suspension. When addition was complete,the reaction mixture was warmed to room temperature and was stirred for3 hours. The mixture was cooled to 2° C. and an additional portion ofCD₃MgI solution (0.4 mL, 0.4 mmol) was added. The mixture was allowed towarm to room temperature and was stirred an additional 3 hours. Thereaction was quenched with 1N HCl (4 mL) and diluted with H₂O (10 mL)resulting in a slightly yellow solution that was extracted with CH₂Cl₂(3×, 200 mL). The combined organic extracts were dried over Na₂SO₄,filtered, and concentrated under reduced pressure to a yellow oil. Thecrude product was purified using an Analogix automated chromatographysystem eluting with 100% CH₂Cl₂ for 8 minutes and then a gradient of0-5% MeOH/CH₂Cl₂ over 40 minutes. The desired product elutes first atabout 22 minutes, followed by unreacted starting material. Fractionscontaining the desired product were concentrated under reduced pressureto a yellow oil that solidified upon standing. The solid was trituratedwith hexane (25 mL) and collected via vacuum filtration to give 0.33 g(53%) of Compound 99 as a white solid, mp 93.7-94.4° C. Fractionscontaining unreacted starting material were also collected andconcentrated to give 0.21 g of 58 as a clear, colorless oil. Therecovered material was re-subjected to the above alkylation reaction togive, after workup and purification, an additional 0.06 g (33%, 62%overall based on total starting material) of Compound 99, mp 93.3-94.0°C. ¹H-NMR (300 MHz, CDCl₃): δ 1.64-1.68 (m, 4H), 2.50 (t, J=7.0, 2H),3.58 (s, 3H), 4.02 (t, J=7.0, 2H), 7.51 (s, 1H). ¹³C-NMR (75 MHz,CDCl₃): δ 21.16, 27.65, 29.91, 41.03, 43.41, 107.87, 141.62, 149.00,151.69, 155.50, 209.12. HPLC (method: Waters Atlantis T3 2.1×50 mm 3 μmC18-RP column—gradient method 5-95% ACN+0.1% formic acid in 14 min (1.0mL/min) with 4 min hold at 95% ACN+0.1% formic acid; Wavelength: 305nm): retention time: 3.24 min; 99.0% purity. MS (M+H): 285.3, (M+Na):307.2. Elemental Analysis (C₁₃H₁₂D₆N₄O₃): Calculated: C=54.92, H=6.38,N=19.71. Found: C=54.85, H=6.36, N=19.49.

Notable in the ¹H-NMR spectrum above was the absence of a singlet ataround 2.15 ppm indicating an absence of methyl ketone hydrogens. Due tothe presence of a triplet at 4.01 ppm in the above ¹H-NMR spectrum,determination of the presence or absence of a singlet peak at around3.99 ppm corresponding to the presence or absence of hydrogens on theN-methyl group at the 7 position (R¹) of the purine ring was notpossible.

Example 6 Synthesis of(±)8-d₁-1-(4,4,6,6,6-d₅-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 419)

(±)8-d₁-1-(4,4,6,6,6-d₅-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 419)

Compound 409 (0.50 g, 1.7 mmol, 1.0 equiv, see Example 2) was dissolvedin EtOD (13 mL, Aldrich 99.5 atom % D) and NaBH₄ (0.07 g, 1.9 mmol, 1.1equiv) was added. An increase in temperature from 24 to 28° C. wasobserved. The reaction was stirred 2 hours at room temperature, then wasquenched by the addition of D₂O (30 mL, Cambridge Isotope Labs, 99 atom% D). A white suspension formed that was extracted with MTBE (4×, 200 mLtotal). The combined organic extracts were dried over Na₂SO₄, filtered,and concentrated under reduced pressure to a clear, colorless oil (0.45g). The crude product was purified by silica gel chromatography elutingfirst with 1% MeOH/CH₂Cl₂ followed by a gradient of 1-5% MeOH/CH₂Cl₂.Fractions containing product were concentrated under reduced pressure togive (0.41 g, 83%) of Compound 419 as a clear colorless oil thatsolidified on standing.

Example 7 Chiral Separation of(R)-8-d₁-1-(4,4,6,6,6-d₅-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 419(R)) and(S)-8-d₁-1-(4,4,6,6,6-d₅-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 419(S))

Separation of Enantiomers of Compound 419.

Compound 419 obtained from Example 6 above (0.38 g) was dissolved in aminimal amount of iPrOH (6 mL, HPLC grade, heating required) and dilutedwith hexane (4 mL, HPLC grade). Enantiomeric separation was achievedusing a Waters HPLC system equipped with a preparative Daicel ChiralpakAD column (20×250 mm). For the first minute of the run, the mobile phasewas 80% hexane and 20% iPrOH along with 0.1% diethylamine. After thefirst minute a gradient to 75% hexane and 25% iPrOH along with 0.1%diethylamine over 15 minutes was used, followed by holding at thissolvent ratio for 17 minutes at a flow rate of 18 mL/min. This methodresulted in baseline separation with 419(R) eluting first (21.0 min),followed by 419(S) (24.1 min). Fractions containing each enantiomer wereconcentrated under reduced pressure to give 0.16 g each of 419(R) (mp107.8-108.8° C.) and 419(S) (mp 108.3-108.4° C.) as off-white solids.

A).(R)-8-d₁-1-(4,4,6,6,6-d₅-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 419(R))

¹H-NMR (300 MHz, CDCl₃): δ 1.36-1.50 (m, 2H), 1.60-1.74 (m, 3H), 3.58(s, 3H), 3.80 (s, 1H), 4.02 (t, J=7.3, 2H). ¹³C-NMR (75 MHz, CDCl₃): δ22.70, 27.86, 29.71, 41.14, 67.66, 107.66, 148.78, 151.54, 155.40. HPLC(method: Waters Atlantis T3 2.1×50 mm 3 μM C18-RP column—gradient method5-95% ACN+0.1% formic acid in 14 min (1.0 mL/min) with 4 min hold at 95%ACN+0.1% formic acid; Wavelength: 254 nm): retention time: 3.26 min;99.9% purity. Chiral HPLC (method: Chiralpak AD 25 cm column—isocraticmethod 78% hexane/22% isopropanol/0.01% diethylamine for 40 min at 1.00mL/min; Wavelength: 254 nm): retention time: 27.51 min (majorenantiomer); 31.19 min (expected for minor enantiomer): >99.9% eepurity. MS (M+H): 290.1, (M+Na): 312.3. Elemental Analysis(C₁₃H₁₁D₉N₄O₃): Calculated: C=53.97, H=6.97, N=19.36. Found: C=54.39,H=7.11, N=18.98.

Notable in the ¹H-NMR spectrum above was the absence of the followingpeaks: a peak at around 1.19 ppm indicating an absence of methylhydrogens alpha to the hydroxyl group; and a singlet at around 7.51 ppmindicating an absence of hydrogen at the number 8 position on the purinering. Due to the presence of a multiplet at 1.36-1.50 ppm and a tripletat 4.01 ppm in the above ¹H-NMR spectrum, determination of the presenceor absence a peak at 1.51 ppm corresponding to the presence or absenceof methylene hydrogens alpha to the hydroxyl group and of a singlet peakat around 3.99 ppm corresponding to the presence or absence of hydrogenson the N-methyl group at the 7 position (R¹) of the purine ring was notpossible.

B).(S)-8-d₁-1-(4,4,6,6,6-d₅-5-Hydroxyhexyl)-3-methyl-7-(methyl-d?)-1H-purine-2,6(3H,7H)-dione(Compound 419(S))

¹H-NMR (300 MHz, CDCl₃): δ 1.41-1.48 (m, 2H), 1.64-1.72 (m, 3H), 3.58(s, 3H), 3.79 (s, 1H), 4.02 (t, J=7.4, 2H). ¹³C-NMR (75 MHz, CDCl₃): δ22.70, 27.86, 29.71, 41.15, 67.66, 107.67, 148.78, 151.54, 155.41. HPLC(method: Waters Atlantis T3 2.1×50 mm 3 μm C18-RP column—gradient method5-95% ACN+0.1% formic acid in 14 min (1.0 mL/min) with 4 min hold at 95%ACN+0.1% formic acid; Wavelength: 254 nm): retention time: 3.26 min;99.9% purity. Chiral HPLC (method: Chiralpak AD 25 cm column—isocraticmethod 78% hexane/22% isopropanol/0.01% diethylamine for 40 min at 1.00mL/min; Wavelength: 254 nm): retention time: 31.19 min (majorenantiomer); 27.51 min (expected for minor enantiomer): >99.9% eepurity. MS (M+H): 290.1, (M+Na): 312.3. Elemental Analysis(C₁₃H₁₁D₉N₄O₃): Calculated: C=53.97, H=6.97, N=19.36. Found: C=54.35,H=7.28, N=18.75.

Notable in the ¹H-NMR spectrum above was the absence of the followingpeaks: a peak at around 1.19 ppm indicating an absence of methylhydrogens alpha to the hydroxyl group; and a singlet at around 7.51 ppmindicating an absence of hydrogen at the number 8 position on the purinering. Due to the presence of a multiplet at 1.36-1.50 ppm and a tripletat 4.01 ppm in the above ¹H-NMR spectrum, determination of the presenceor absence a peak at 1.51 ppm corresponding to the presence or absenceof methylene hydrogens alpha to the hydroxyl group and of a singlet peakat around 3.99 ppm corresponding to the presence or absence of hydrogenson the N-methyl group at the 7 position (R¹) of the purine ring was notpossible.

Example 8 Synthesis of(±)8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3-methyl-7-(methyl-4)-1H-purine-2,6(3H,7H)-dione(Compound 435)

(±)8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 435)

To a solution of Compound 409 (0.50 g, 1.7 mmol, 1.0 equiv) in EtOD (13mL, Aldrich 99.5 atom % D) was added NaBD₄ (0.08 g, 1.9 mmol, 1.1 equiv,Cambridge Isotope Labs, 99 atom % D). An increase in temperature from 24to 27° C. was observed. The reaction was stirred 2 hours at roomtemperature then was quenched by the addition of D₂O (30 mL) (CambridgeIsotope, 99 atom % D). A white suspension formed that was extracted withMTBE (4×, 200 mL total). The combined organic extracts were dried overNa₂SO₄, filtered, and concentrated under reduced pressure to a clear,colorless oil (0.45 g). The crude product was purified by silica gelchromatography eluting first with 1% MeOH/CH₂Cl₂ followed by a gradientof 1-5% MeOH/CH₂Cl₂. Fractions containing product were concentratedunder reduced pressure to give 0.40 g (81%) of Compound 435 as a clearcolorless oil that solidified on standing.

Example 9 Chiral Separation of(R)-8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 435(R)) and(S)-8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 435(S))

Separation of Enantiomers of Compound 435.

Compound 435 obtained from Example 8 above (0.32 g) was dissolved in aminimal amount of iPrOH (5 mL, HPLC grade, heating was required) anddiluted with hexane (4 mL, HPLC grade). Enantiomer separation wasachieved using a Waters HPLC system equipped with a preparative DaicelChiralpak AD column (20×250 mm). For the first minute of the run, themobile phase was 80% hexane and 20% iPrOH along with 0.1% diethylamine.After the first minute a gradient to 75% hexane and 25% iPrOH along with0.1% diethylamine over 15 minutes was used, followed by holding at thissolvent ratio for 17 minutes at a flow rate of 18 mL/min. This methodresulted in baseline separation with Compound 435(R) eluting first (21.9min), followed by Compound 435(S) (25.2 min). Fractions containing eachenantiomer were concentrated under reduced pressure to give 0.12 g eachof 435(R) (mp 108.0-108.1° C.) and 435(S) (mp107.6-107.7° C.) asoff-white solids.

A).(R)-8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 435(R))

¹H-NMR (300 MHz, CDCl₃): δ 1.40-1.48 (m, 3H), 1.66-1.70 (m, 2H), 3.58(s, 3H), 4.02 (t, J=7.5, 2H). ¹³C-NMR (75 MHz, CDCl₃): δ 22.66, 27.86,29.71, 41.15, 107.67, 148.80, 151.54, 155.41. HPLC (method: WatersAtlantis T3 2.1×50 mm 3 μm C18-RP column—gradient method 5-95% ACN+0.1%formic acid in 14 min (1.0 mL/min) with 4 min hold at 95% ACN+0.1%formic acid; Wavelength: 254 nm): retention time: 3.25 min; 99.8%purity. Chiral HPLC (method: Chiralpak AD 25 cm column—isocratic method78% hexane/22% isopropanol/0.01% diethylamine for 40 min at 1.00 mL/min;Wavelength: 254 nm): retention time: 27.24 min (major enantiomer); 31.11min (expected for minor enantiomer): >99.9% ee purity. MS (M+H): 291.3,(M+Na): 313.2. Elemental Analysis (C₁₃H₁₀D₁₀N₄O₃): Calculated: C=53.78,H=6.94, N=19.30. Found: C=54.01, H=7.07, N=18.90.

Notable in the ¹H-NMR spectrum above was the absence of the followingpeaks: a peak at around 1.19 ppm indicating an absence of methylhydrogens alpha to the hydroxyl group; a peak at around 3.80 ppmindicating an absence of hydrogen at the methinyl hydroxyl position; anda singlet at around 7.51 ppm indicating an absence of hydrogen at thenumber 8 position on the purine ring. Due to the presence of a multipletat 1.36-1.50 ppm and a triplet at 4.01 ppm in the above ¹H-NMR spectrum,determination of the presence or absence a peak at 1.51 ppmcorresponding to the presence or absence of methylene hydrogens alpha tothe hydroxyl group and of a singlet peak at around 3.99 ppmcorresponding to the presence or absence of hydrogens on the N-methylgroup at the 7 position (R¹) of the purine ring was not possible.

B).(S)-8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3-methyl-7-(methyl-4)-1H-purine-2,6(3H,7H)-dione(Compound 435(S))

¹H-NMR (300 MHz, CDCl₃): δ 1.41-1.48 (m, 3H), 1.62-1.72 (m, 2H), 3.58(s, 3H), 4.03 (t, J=7.4, 2H). ¹³C-NMR (75 MHz, CDCl₃): δ 22.69, 27.90,29.70, 41.17, 107.69, 148.82, 151.58, 155.43. HPLC (method: WatersAtlantis T3 2.1×50 mm 3 μm C18-RP column—gradient method 5-95% ACN+0.1%formic acid in 14 min (1.0 mL/min) with 4 min hold at 95% ACN+0.1%formic acid; Wavelength: 254 nm): retention time: 3.25 min; 99.5%purity. Chiral HPLC (method: Chiralpak AD 25 cm column—isocratic method78% hexane/22% isopropanol/0.01% diethylamine for 40 min at 1.00 mL/min;Wavelength: 254 nm): retention time: 31.11 min (major enantiomer); 27.24min (expected for minor enantiomer): >99.9% ee purity. MS (M+H): 291.3,(M+Na): 313.2. Elemental Analysis (C₁₃H₁₀D₁₀N₄O₃): Calculated: C=53.78,H=6.94, N=19.30. Found: C=54.01, H=7.11, N=18.78.

Notable in the ¹H-NMR spectrum above was the absence of the followingpeaks: a peak at around 1.19 ppm indicating an absence of methylhydrogens alpha to the hydroxyl group; a peak at around 3.80 ppmindicating an absence of hydrogen at the methinyl hydroxyl position; anda singlet at around 7.51 ppm indicating an absence of hydrogen at thenumber 8 position on the purine ring. Due to the presence of a multipletat 1.36-1.50 ppm and a triplet at 4.01 ppm in the above ¹H-NMR spectrum,determination of the presence or absence a peak at 1.51 ppmcorresponding to the presence or absence of methylene hydrogens alpha tothe hydroxyl group and of a singlet peak at around 3.99 ppmcorresponding to the presence or absence of hydrogens on the N-methylgroup at the 7 position (R¹) of the purine ring was not possible.

Example 10 Synthesis of8-d₁-3,7-Dimethyl-1-(4,4,6,6,6-d₅-5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 407)

8-d₁-3,7-Dimethyl-1-(4,4,6,6,6-d₅-5-oxohexyl)-1H-purine-2,6(3H,7H)-dione(Compound 407)

A mixture of commercially-available 59 (7.95 g, 28.6 mmol) and potassiumcarbonate (990 mg, 7.2 mmol) in D₂O (195 mL, Cambridge Isotopes, 99.9atom % D) was heated to reflux for 24 hours. The suspended soliddissolved gradually giving a yellow solution. The solution was cooled toapproximately 40° C. and was concentrated under reduced pressure to atan solid. The solid was dissolved in D₂O (195 mL) and the solution washeated to reflux for another 24 hours. The solution was cooled to roomtemperature and concentrated under reduced pressure to a tan solid.Ethyl acetate (200 mL) was added and the mixture was stirred 0.5 hoursat approximately 40° C. The insoluble materials were filtered off andthe filtrate was concentrated under reduced pressure to a pale yellowsolid, which was triturated with MTBE (40 mL) to give 7.5 g (93%) ofCompound 407 as an off-white solid. ¹H-NMR (300 MHz, CDCl₃): δ 1.64-1.68(m, 4H), 3.57 (s, 3H), 3.99 (s, 3H), 3.99-4.04 (m, 2H). ¹³C-NMR (75 MHz,CDCl₃): δ 20.84, 27.40, 29.69, 33.57, 40.81, 107.62, 148.77, 151.48,155.28, 209.07. HPLC (method: Waters Atlantis T3 2.1×50 mm 3 μm C18-RPcolumn—gradient method 5-95% ACN+0.1% formic acid in 14 min (1.0 mL/min)with 4 min hold at 95% ACN+0.1% formic acid; Wavelength: 305 nm):retention time: 3.24 min; 99.9% purity. MS (M+H): 285.3, (M+Na): 307.2.Elemental Analysis (C₁₃H₁₂D₆N₄O₃): Calculated: C=54.92, H=6.38, N=19.71.Found: C=54.89, H=6.38, N=19.70.

Notable in the ¹H-NMR spectrum above was the absence of the followingpeaks: a singlet at around 2.15 ppm indicating an absence of methylketone hydrogens; a triplet at around 2.51 ppm indicating an absence ofmethylene ketone hydrogens; and a singlet at around 7.52 ppm indicatingan absence of hydrogen at the number 8 position on the purine ring.

Example 11 Synthesis of(±)8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3,7-dimethyl-1H-purine-2,6(3H,7H)-dione(Compound 437)(±)8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3,7-dimethyl-1H-purine-2,6(3H,7H)-dione(Compound 437)

Sodium borodeuteride (1.06 g, 25.3 mmol, Cambridge Isotopes, 99 atom %D) was added to a suspension of 407 (6.5 g, 22.9 mmol) in ethanol-d₁ (65mL, Aldrich, 99.5 atom % D) at 0° C. The mixture was warmed to roomtemperature and stirred until a clear solution had developed(approximately 1 hour). The reaction was quenched with a saturatedsolution of ammonium chloride-d₄ (Cambridge Isotopes, 98 atom % D) inD₂O (8 mL, Cambridge Isotope, 99.9 atom % D), ethanol-d₁ was evaporatedunder reduced pressure and the residue was extracted with EtOAc (160mL). The organic phase was washed with D₂O (20 mL), dried over sodiumsulfate, filtered and concentrated under reduced pressure to give 4.8 g(73%) of Compound 437 as a pale yellow solid.

Example 12 Chiral Separation of(R)-8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3,7-dimethyl-1H-purine-2,6(3H,7H)-dione(Compound 437(R)) and(S)-8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3,7-dimethyl-1H-purine-2,6(3H,7H)-dione(Compound 437(S))

Separation of Enantiomers of Compound 437.

Compound 437 obtained from Example 11 above (1.60 g) was dissolved iniPrOH (20 mL, HPLC grade, heating required). Enantiomeric separation wasachieved using a Waters HPLC system equipped with a preparativeChiralpak AD column (20×250 mm Daicel, 10 μM) with a preparativeChiralpak AD guard column (20×50 mm Daicel, 10 μM) preceding it. For thefirst minute of the run, the sample was eluted with 20% iPrOH/hexanes(henceforth, with 0.1% diethylamine as co-eluent) while ramping up froma flow rate of 15 mL/min to 18 mL/min. Over the next 15 minutes, thesample was eluted at a flow rate of 18 mL/min with a gradient of 20% to25% iPrOH/hexanes. For the next 19 minutes the sample was eluted at aflow rate of 18 mL/min with 25% iPrOH/hexanes. Over the next 0.5minutes, the sample was eluted at a flow rate of 18 mL/min with agradient of 25% to 20% iPrOH/hexanes. For the next 4.5 minutes, thesample was eluted at a flow rate of 18 mL/min with 20% iPrOH/hexanes.This elution method resulted in baseline separation of Compound 437(R)eluting first (retention time approximately 29 min) and Compound 437(S)eluting second (retention time approximately 33 min). Fractionscontaining each enantiomer were collected and concentrated under reducedpressure to give 340 mg of 437(R) (mp 112.0-114.5° C.) and 375 mg of437(S) (mp 111.9-112.3° C.) as off-white solids. [Note: only 1.0 g of437 was injected from the solution prepared above.]

A.(R)-8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3,7-dimethyl-1H-purine-2,6(3H,7H)-dione(Compound 437(R))

¹H-NMR (300 MHz, CDCl₃): δ 1.36-1.50 (m, 2H), 1.54 (s, 1H), 1.64-1.74(m, 2H), 3.58 (s, 3H), 3.99 (s, 3H), 4.00-4.05 (m, 2H). ¹³C-NMR (75 MHz,CDCl₃): 622.66, 27.86, 29.70, 33.59, 41.14, 107.65, 148.76, 151.52,155.40. HPLC (method: Waters Atlantis T3 2.1×50 mm 3 μm C18-RPcolumn—gradient method 5-95% ACN+0.1% formic acid in 14 min (1.0 mL/min)with 4 min hold at 95% ACN+0.1% formic acid; Wavelength: 305 nm):retention time: 3.28 min; 99.9% purity. Chiral HPLC (method: ChiralpakAD 25 cm column—isocratic method 78% hexane/22% isopropanol/0.01%diethylamine for 40 min at 1.00 mL/min; Wavelength: 254 nm): retentiontime: 25.20 min (major enantiomer); 28.39 min (expected for minorenantiomer): >99.9% ee purity. MS (M+H): 288.3, (M+Na): 310.2. ElementalAnalysis (C₁₃H₁₃D₇N₄O₃): Calculated: C=54.34, H=7.02, N=19.50. Found:C=54.32, H=7.23, N=19.35.

Notable in the ¹H-NMR spectrum above was the absence of the followingpeaks: a peak at around 1.19 ppm indicating an absence of methylhydrogens alpha to the hydroxyl group; a peak at around 3.80 ppmindicating an absence of hydrogen at the methinyl hydroxyl position; anda singlet peak at around 7.51 ppm indicating an absence of hydrogen atthe number 8 position on the purine ring. Due to the presence of amultiplet at 1.36-1.50 ppm in the above ¹H-NMR spectrum, determinationof the presence or absence a peak at 1.51 ppm corresponding to thepresence or absence of methylene hydrogens alpha to the hydroxyl groupwas not possible.

B.(S)-8-d₁-1-(4,4,5,6,6,6-d₆-5-Hydroxyhexyl)-3,7-dimethyl-1H-purine-2,6(3H,7H)-dione(Compound 437(S))

¹H-NMR (300 MHz, CDCl₃): δ 1.38-1.48 (m, 2H), 1.55 (s, 1H), 1.64-1.72(m, 2H), 3.58 (s, 3H), 3.99 (s, 3H), 4.00-4.05 (m, 2H). ¹³C-NMR (75 MHz,CDCl₃): δ 22.65, 27.84, 29.71, 33.59, 41.13, 107.64, 148.75, 151.52,155.39. HPLC (method: Waters Atlantis T3 2.1×50 mm 3 μm C18-RPcolumn—gradient method 5-95% ACN+0.1% formic acid in 14 min (1.0 mL/min)with 4 min hold at 95% ACN+0.1% formic acid; Wavelength: 305 nm):retention time: 3.27 min; 99.9% purity. Chiral HPLC (method: ChiralpakAD 25 cm column—isocratic method 78% hexane/22% isopropanol/0.01%diethylamine for 40 min at 1.00 mL/min; Wavelength: 254 nm): retentiontime: 28.39 min (major enantiomer); 25.20 min (expected for minorenantiomer): >99.9% ee purity. MS (M+H): 288.3, (M+Na): 310.2. ElementalAnalysis (C₁₃H₁₃D₇N₄O₃): Calculated: C=54.34, H=7.02, N=19.50. Found:C=54.33, H=7.30, N=19.36.

Notable in the ¹H-NMR spectrum above was the absence of the followingpeaks: a peak at around 1.19 ppm indicating an absence of methylhydrogens alpha to the hydroxyl group; a peak at around 3.80 ppmindicating an absence of hydrogen at the methinyl hydroxyl position; anda singlet peak at around 7.51 ppm indicating an absence of hydrogen atthe number 8 position on the purine ring. Due to the presence of amultiplet at 1.36-1.50 ppm in the above ¹H-NMR spectrum, determinationof the presence or absence a peak at 1.51 ppm corresponding to thepresence or absence of methylene hydrogens alpha to the hydroxyl groupwas not possible.

Example 13 Synthesis of(±)1-(5-d₁-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 131)

(±)1-(5-d₁-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 131)

Following the same general method as for the synthesis of Compound 437above, Compound 100 (see Example 1) was treated with NaBD₄ in EtOH toafford Compound 131.

Example 14 Chiral Separation of(R)-1-(5-d₁-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 131(R)) and(S)-1-(5-d₁-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 131(S))

Separation of Enantiomers of Compound 131.

A portion of racemic Compound 131 obtained from Example 13 above wasseparated in the same manner as racemic Compound 437 above, to affordseparated enantiomers Compound 131(R) (mp 112.2-112.7° C.) (210 mg) andCompound 131(S) (mp 112.0-112.1° C.) (220 mg).

A.(R)-1-(5-d₁-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 131(R))

¹H-NMR (300 MHz, CDCl₃): δ 1.19 (s, 3H), 1.39-1.56 (m, 5H), 1.64-1.74(m, 2H), 3.58 (s, 3H), 4.03 (t, J=7.3, 2H), 7.51 (s, 1H). ¹³C-NMR (75MHz, CDCl₃): δ 22.87, 23.40, 27.89, 29.71, 38.64, 41.13, 107.68, 141.40,148.76, 151.52, 155.39. HPLC (method: Waters Atlantis T3 2.1×50 mm 3 μmC18-RP column—gradient method 5-95% ACN+0.1% formic acid in 14 min (1.0mL/min) with 4 min hold at 95% ACN+0.1% formic acid; Wavelength: 305nm): retention time: 3.29 min; 99.9% purity. Chiral HPLC (method:Chiralpak AD 25 cm column—isocratic method 78% hexane/22%isopropanol/0.01% diethylamine for 40 min at 1.00 mL/min; Wavelength:254 nm): retention time: 25.14 min (major enantiomer); 28.51 min(expected for minor enantiomer): >99.9% ee purity. MS (M+H): 285.3,(M+Na): 307.2. Elemental Analysis (C₁₃H₁₆D₄N₄O₃): Calculated: C=54.92,H=7.09, N=19.71. Found: C=54.67, H=7.04, N=19.35.

Notable in the ¹H-NMR spectrum above was the absence of a peak at around3.80 ppm indicating an absence of hydrogen at the methinyl hydroxylposition. Due to the presence of a triplet at 4.01 ppm in the above¹H-NMR spectrum, determination of the presence or absence of a singletpeak at around 3.99 ppm corresponding to the presence or absence ofhydrogens on the N-methyl group at the 7 position (R¹) of the purinering was not possible.

B.(S)-1-(5-d₁-5-Hydroxyhexyl)-3-methyl-7-(methyl-d₃)-1H-purine-2,6(3H,7H)-dione(Compound 131(S))

¹H-NMR (300 MHz, CDCl₃): δ 1.18 (s, 3H), 1.39-1.55 (m, 5H), 1.67-1.72(m, 2H), 3.58 (s, 3H), 4.03 (t, J=7.3, 2H), 7.51 (s, 1H). ¹³C-NMR (75MHz, CDCl₃): δ 23.10, 23.63, 28.12, 29.94, 38.87, 41.36, 107.91, 141.63,148.99, 151.75, 155.62. HPLC (method: Waters Atlantis T3 2.1×50 mm 3 μmC18-RP column—gradient method 5-95% ACN+0.1% formic acid in 14 min (1.0mL/min) with 4 min hold at 95% ACN+0.1% formic acid; Wavelength: 305nm): retention time: 3.29 min; 99.9% purity. Chiral HPLC (method:Chiralpak AD 25 cm column—isocratic method 78% hexane/22%isopropanol/0.01% diethylamine for 40 min at 1.00 mL/min; Wavelength:254 nm): retention time: 28.51 min (major enantiomer); 25.14 min(expected for minor enantiomer): >99.9% ee purity. MS (M+H): 285.3,(M+Na): 307.2. Elemental Analysis (C₁₃H₁₆D₄N₄O₃): Calculated: C=54.92,H=7.09, N=19.71. Found: C=54.65, H=7.04, N=19.32.

Notable in the ¹H-NMR spectrum above was the absence of a peak at around3.80 ppm indicating an absence of hydrogen at the methinyl hydroxylposition. Due to the presence of a triplet at 4.01 ppm in the above¹H-NMR spectrum, determination of the presence or absence of a singletpeak at around 3.99 ppm corresponding to the presence or absence ofhydrogens on the N-methyl group at the 7 position (R¹) of the purinering was not possible.

Biological Evaluation Example 15a Evaluation of Pharmacokinetics in DogsFollowing Oral Administration. Comparison of Compound 409 andPentoxifylline

Metabolism of the title compounds were studied following oraladministration to male beagle dogs. Blood samples were removed fromdosed dogs at various time points and plasma isolated therefrom. Theplasma samples were used for the determination of plasma drug levels byLC-MS/MS (liquid chromatography with tandem mass spectrometry) forestimating pharmacokinetic parameters.

Compound 409 and pentoxifylline were dissolved separately in saline to aconcentration of 4 mg/mL. A 1:1 (v/v) mixture of the two solutions wasprepared to yield a solution having a final concentration of 2 mg/mL ofboth Compound 409 and pentoxifylline.

Two male beagle dogs were fasted overnight and then orally dosed viagavage with 2.5 mg/kg of Compound 409 and pentoxifylline using themixture described above. Blood samples (1.5-2 mL) were collected via thefemoral vein at 0 min (pre-dose), 15 min, 30 min, 45 min, 1 hr, 1.5 hr,2 hr, 3 hr, 4 hr, 6 hr, 8 hr, 10 hr, 12 hr, 16 hr and 24 hr post-dose.Blood was stored on ice prior to centrifugation to obtain plasmasamples. Centrifugation took place within 1 hour of blood collection toharvest plasma (maximum volume). The plasma was decanted immediately andfrozen/stored at −70° C. until analysis.

TABLE 8 Plasma Levels of Compound 409 vs Pentoxifylline in Dogs (Example15a) Compound Ave. Cmax (ng/mL) Ave. AUC (hr*ng/mL) Pentoxifylline  784448 Compound 409 1230 811 % Difference^(a) +57% +80% ^(a)% Difference =[(deuterated species) − (nondeuterated species)](100)/(nondeuteratedspecies)

Table 8 shows the results of the evaluation described in Example 15a.The average C_(max) and average AUC for Compound 409, a deuteratedversion of pentoxifylline, were significantly greater than forpentoxifylline. The deuterated compound exhibited greater exposure inthe dog plasma than pentoxifylline.

Example 15b Repeat Evaluation of Pharmacokinetics in Dogs Following OralAdministration. Comparison of Compound 409 and Pentoxifylline withMonitoring of Metabolites

Example 15a was repeated with additional monitoring of thepentoxifylline and Compound 409 metabolites. In this experiment Compound409 and pentoxifylline were dissolved separately in saline to aconcentration of 4.4 and 4 mg/mL respectively. A 1:1 (v/v) mixture ofthe two solutions was prepared to yield a solution having a finalconcentration of 2.2 mg/mL of Compound 409 and 2 mg/mL pentoxifylline.Post-dosing data analysis included adjustments to account for the 10%difference in dosing concentration between compound 409 andpentoxifylline.

Four beagle dogs (2-3 years of age, and weighed 5 to 8 kg) were fastedovernight and then orally dosed via gavage with 2.75 mg/kg Compound 409and 2.5 mg/kg pentoxifylline using the mixture described above. Bloodsamples (approximately 1 mL) were collected via femoral vein at 0 min(pre-dose), 5 min, 15 min, 30 min, 45 min, 1 hr, 1.5 hr, 2 hr, 3 hr, 4hr, and 6 hr post-dose. Blood was stored on ice prior to centrifugationto obtain plasma samples. Centrifugation took place within 15 minutes ofblood collection to harvest plasma (maximum volume). The plasma wasdecanted immediately and frozen/stored at −20° C. until analysis.

Plasma samples were analyzed by LC-MS/MS for the presence of theadministered compound and its corresponding M1 metabolite:

The results from each of the four dogs are shown in FIGS. 1A and 1B. Theresults from one of the four dogs (Dog H, FIG. 1 b) were inconsistentwith that of the other three. That dog showed a 10-fold higher plasmaconcentration of each of the administered compounds and their respectivemetabolites at 5 minutes post-administration. In addition, that dog didnot show a characteristic increase in plasma concentration of theadministered compounds between 5 and 15 minutes post-administration. Itwas concluded that this dog was most likely improperly gavaged and thatthe compounds were probably administered through the trachea, ratherthan into the GI tract as would have been desired. Accordingly, the datafrom this dog was excluded from the analyses. The summary analysis ofthe three remaining dogs is shown in Table 9.

TABLE 9 Plasma Levels of Compound 409 vs Pentoxifylline in Dogs (Example15b) Compound Ave. C_(max) (ng/mL) Ave. AUC (hr*ng/mL) Pentoxifylline166  69 Compound 409^(a) 299 136 % Difference^(b) +80% +97% ^(a)Thedosing concentration of compound 409 was 10% higher than that forpentoxifylline and thus the numbers reported here reflect the adjustmentfor that 10% increase. ^(b)% Difference = [(deuterated species) −(nondeuterated species)](100)/(nondeuterated species)

As can be seen in Table 9, higher levels of Compound 409 in terms ofC_(max) and AUC were observed when compared to pentoxifylline co-dosedat the same level. FIG. 1 demonstrates that Compound 409 was more slowlycleared from the plasma than pentoxifylline in the three dogs that wereorally dosed. FIGS. 1 a and 1 b demonstrate that Compound 409 was moreslowly cleared from the plasma than pentoxifylline in the three dogsthat were orally dosed. FIGS. 1 a and 1 b also show that overallsystemic exposure to Compound 419 (the deuterated M1 metabolite of 409)following dosing of Compound 409 was greater than that of the M1metabolite following dosing of pentoxifylline.

Example 15c Evaluation of Pharmacokinetics in Dogs Following OralAdministration. Comparison of Compound 413 and Pentoxifylline

This study was similar to those described in Examples 15a and 15b,except that Compound 413 was evaluated. Four male beagle dogs wereorally dosed by gavage with a mixture containing 2 mg/mL each ofpentoxifylline and Compound 413 in saline. Blood samples were taken asin Example 15b.

TABLE 10 Plasma Levels of Compound 413 vs Pentoxifylline in Dogs(Example 15c) Compound Ave. Cmax (ng/mL) Ave. AUC (hr*ng/mL)Pentoxifylline 369 238 Compound 413 542 415 % Difference^(a) +47% +74%^(a)% Difference = [(deuterated species) − (nondeuteratedspecies)](100)/(nondeuterated species)

The results of this study are summarized in Table 10 above. The tabledepicts the plasma levels of Compound 413 compared to pentoxifyllinefollowing oral dosing. Higher levels of Compound 413 in terms of C_(max)and AUC were observed when compared to pentoxifylline co-dosed at thesame level.

Example 16 Evaluation of the Stability of Compounds in Rat Whole Blood.Comparison of Compounds 409, 435(S), 435(R) and Pentoxifylline and itsM-1 Metabolites

This study was performed to evaluate the stability of the titlecompounds in rat whole blood. Because the ketone (or keto-compound;either pentoxifylline or 409) and its corresponding M-1 alcoholmetabolite interconvert, levels of these components were measured aftereither the keto-compound was added to the blood or the M-1 was added. Inother words, in some tests the keto-compound was the starting testcompound and in other tests an M-1 metabolite was the starting testcompound.

Fresh rat whole blood was obtained from ViviSource Laboratories,Waltham, Mass. Stock solutions (7.5 millimolar (mM)) of test compoundswere prepared in dimethyl sulfoxide (DMSO). The 7.5 mM stock solutionswere diluted to 500 micromolar (μM) in acetonitrile (ACN). To 990microliters (μL) of blood pre-warmed to 37° C. for 7 minutes was added10 μL of 500 μM test compound to a final concentration of 5 μM. The testcompounds were pentoxifylline, (S)-M1 metabolite of pentoxifylline,(R)-M1 metabolite of pentoxifylline, Compound 409, Compound 435(S), andCompound 435(R). The latter two test compounds are deuterated (S)-M1 and(R)-M1 metabolites, respectively, of Compound 409. The reaction mixturewas incubated at 37° C. Aliquots (50 μL) were removed at 0 min, 5 min,15 min, 30 min, 1 hour and 2 hours following the addition of testcompound and added to 96-well plates containing 150 μL of ice coldacetonitrile with an internal standard to stop the reaction. The plateswere stored at −20° C. for 20 minutes after which 100 μL of 50%acetonitrile/water was added to the wells of the plate prior tocentrifugation to pellet precipitated proteins. A 200-μL aliquot of eachsupernatant was transferred to another 96-well plate and analyzed byLC-MS/MS using an Applied Bio-systems API 4000 mass spectrometer foramounts of the administered compound and its specific metabolite listedin Table 11 below.

TABLE 11 Compound-Metabolite Pairs Analyzed in Rat Whole Blood.(Experiments 16 and 17) Compound Incubated with Experiment Pair BloodMetabolite Analyzed A pentoxifylline (S)-M1^(a) B Compound 409 Compound419(S)^(a) C (S)-M1 pentoxifylline D Compound 435(S) Compound 409 E(R)-M1 pentoxifylline F Compound 435(R) Compound 409 ^(a)Mass observedvia LC-MS/MS. Stereochemistry presumed to be ≧95% (S) based on publishedpentoxifylline metabolism reports.

The results of this study are depicted in FIGS. 2 and 3. The time courseof metabolite formation is shown in FIG. 2. The relative amount ofmetabolite formed, as shown in FIG. 3, was calculated based on theamount present at 2 hr relative to the earliest time point at which itwas detected in the incubation mixture, 5 minutes for A and B, and 15minutes for C.

As seen in FIG. 3, after approximately 2 hours the amount of (5)-M1formed in rat whole blood incubated with pentoxifylline (FIG. 3, columnA) was similar to the amount of Compound 419(S) formed in rat wholeblood incubated with Compound 409 (FIG. 3, column B). Thus, thedeuterium substitution in Compound 409 had no discernable effect on therelative level of deuterated (S)-M1 metabolite (Compound 419(S)) formedas compared to the relative level of undeuterated (S)-M1 formed fromundeuterated pentoxifylline.

For the reverse reaction, (5)-M1 to the keto-compound, deuteration didhave a significant effect. Column C in FIG. 3 shows an appreciableamount of pentoxifylline present after addition of (S)-M1. By contrast,2 hours after addition of Compound 435 (S), Compound 409 was notdetected (FIG. 3, column D). Under these conditions, the deuteriumsubstitution in Compound 435 (S) impedes the conversion of this compoundto the corresponding ketone. Such an effect is particularly beneficialfor enhancing the plasma levels of the desired M-1 metabolite.

No metabolism of (R)-M1 to pentoxifylline was detected in this assay.Similarly, Compound 409 was not detected after addition of Compound 435(R) to the rat blood. Thus, no conclusions could be made concerning theeffect of deuteration on the conversion of (R)-M1 to pentoxifylline.FIG. 2 shows the time course of the specific metabolite produced duringincubation of the administered compound with rat whole blood.

Example 17 Evaluation of Compound Stability in Human Liver Microsomes.Comparison of Compounds 409, 435(S), 435(R) and Pentoxifylline

Example 17 is similar to Example 16 in design, except that human livermicrosomes were used instead of rat whole blood to study the metabolismof the compounds. Table 11 above shows each pair of test compound andmetabolite that was analyzed in this Example 17.

Human liver microsomes (20 mg/mL) were obtained from Xenotech, LLC(Lenexa, Kans.). β-nicotinamide adenine dinucleotide phosphate, reducedform (NADPH), magnesium chloride (MgCl₂), and dimethyl sulfoxide (DMSO)were purchased from Sigma-Aldrich.

Stock solutions containing 7.5 mM of test compounds (pentoxifylline,(S)-M1 metabolite, (R)-M1 metabolite, Compound 409, Compound 435(S), andCompound 435(R)) were prepared in DMSO. The 7.5-mM stock solutions werediluted to 250 μM in acetonitrile (ACN). The human liver microsomes werediluted to 2.5 mg/mL in 0.1 M potassium phosphate buffer, pH 7.4,containing 3 mM MgCl₂. The diluted microsomes were added to wells of a96-well deep-well polypropylene plate in triplicate. 10 μL of the 250 μMtest compound was added to the microsomes and the mixture was pre-warmedto 37° C. for 10 minutes. Reactions were initiated by addition ofpre-warmed NADPH solution. The final reaction volume was 0.5 mL andcontained 2.0 mg/mL human liver microsomes, 5 μM test compound, and 2 mMNADPH in 0.1M potassium phosphate buffer, pH 7.4, and 3 mM MgCl₂. Thereaction mixtures were incubated at 37° C., and 50-μL aliquots wereremoved at 0, 5, 10, 20, and 30 minutes and added to shallow-well96-well plates which contained 50 μL of ice-cold acetonitrile withinternal standard to stop the reactions. The plates were stored at 4° C.for 20 minutes after which 100 μL of water was added to the wells of theplate before centrifugation to pellet precipitated proteins.Supernatants were transferred to another 96-well plate and analyzed forthe amount of the administered compound and its specific metabolite(listed in Table 11 above) by LC-MS/MS using an Applied Bio-systems API4000 mass spectrometer.

The results of this study are depicted in FIGS. 4 and 5. The time courseof metabolite formation is shown in FIG. 4. The relative amount ofmetabolite formed, as shown in FIG. 5, was calculated based on theamount present at 30 minutes relative to the earliest time point atwhich it was detected in the incubation mixture, 0 minutes for A, B, Cand E, 5 minutes for D, and 10 minutes for F. The amount of (S)-M1formed in human liver microsomes incubated with pentoxifylline (FIG. 5,column A) after 30 minutes was similar to the amount Compound 419(5)formed in human liver microsomes incubated with Compound 409 (FIG. 5,column B). Thus, deuteration of pentoxifylline as embodied by Compound409 had no discernable effect on the relative level of deuterated (S)-M1metabolite (Compound 419(S)) formed as compared to the relative level ofundeuterated (S)-M1 formed from undeuterated pentoxifylline. Theseresults in human liver microsomes were consistent with those seen usingrat whole blood.

For the reverse reaction, (S)-M1 to the keto-compound, deuteration didhave an appreciable effect. Column C in FIG. 5 shows a significantamount of pentoxifylline present 30 minutes after addition of (S)-M1. Bycontrast, after addition of Compound 435 (S), the level of Compound 409that was detected after 30 minutes was less than the level of (S)-M1(FIG. 5, column D). Approximately 30% more pentoxifylline was producedfrom (5)-M1 than Compound 409 produced from Compound 435 (S). Underthese conditions, the deuterium substitution in Compound 435 (S) impedesthe conversion of this compound to the corresponding ketone. Whiledeuterium had a greater effect in rat blood, the results are consistent.

A dramatic deuterium effect on the metabolism of (R)-M1 metabolite wasobserved in human liver microsomes. Deuteration of (R)-M1 (Compound435(R)) reduced by almost 5-fold the amount of deuterated pentoxifyllineformed (Compound 409) after 30 minute incubation with human livermicrosomes as compared to the amount of undeuterated pentoxifyllineformed from undeuterated (R)-M1 (comparing columns E and F in FIG. 5).FIG. 4 shows the time course of the specific metabolite produced duringincubation of the administered compound with human liver microsomes.

Example 18 Pharmacokinetic Study in Rats of (S)-M1 and Compound 435(S)After Oral and Intravenous Dosing

(S)-M1 and Compound 435(S) (a deuterated form of (S)-M1) were separatelydissolved in saline at a concentration of 10 mg/mL. A 1:1 mixture of thetwo compounds was then prepared containing a final concentration of 5mg/mL of each compound, which was used for intravenous administration.For oral administration the mixture was further diluted in saline to afinal concentration of 1 mg/mL for each compound.

Three male Sprague-Dawley rats were used in each of the oral andintravenous studies. Animals were fasted overnight prior toadministration of compounds. Intravenous administration was achieved bybolus injection of a single 5 mg/kg dose of the 1:1 combination into thecannulated jugular vein of the rats. Cannulation was achieved the dayprior to dosing on rats that had been placed under anesthesia usingketamine (IM 30 mg/kg). Oral administration was achieved by oral gavageof a single 5 mg/kg dose. Blood samples (250 μL) were collected from thedosed rats at various times post-dosing (2 min, 5 min, 10 min, 20 min,30 min, 1 hr, 2 hr, 3 hr, 4 hr, 5 hr, 6 hr) by retro-orbital sampling ofthe rats temporarily anesthetized with isoflurane. Blood samples wereplaced in tubes containing K₂-EDTA and stored on ice until centrifuged.Within 30 minutes of collection, plasma was isolated by centrifugation.A 100-μL aliquot was removed, mixed with 200 μL of acetonitrile andstored at −20° C. until further analysis by LC-MS/MS using an AppliedBio-systems API 4000 mass spectrometer.

Samples were analyzed for the presence of the administered compound, thecorresponding ketone (pentoxifylline and Compound 409) and thecorresponding M5 metabolite. Samples (10 μL) were injected into a ZorbaxSB-C8 (Rapid Resolution) column (2.1×30 mm, 3.5 μm). The initial mobilephase condition was 100% A (10 mM ammonium acetate in water) and 0% B(methanol) with a flow rate at 0.5 mL/min. Mobile phase B was allowed toreach 55% in 3 minutes and from 55% to 90% in 1 minute before rampingback to 0% in another minute. The overall run time was 5 minutes. Forpentoxifylline and its M1 and M5 metabolites, the precursor/product ionpairs were set at m/z 281/193 (M1), m/z 279/181 (pentoxifylline), andm/z 267/221 (M5).

For Compound 435(S) and Compound 409 more than one ion pair was set upfor to detect species that arose from loss of deuterium. It was foundthat some degree of deuterium loss occurs on those compounds of theinvention, such as Compound 409, which have deuterium on the side chainat positions adjacent to the carbonyl carbon. This loss of deuteriumappears to occur both in vivo and ex vivo by an unknown mechanism. Theaddition of acetonitrile to serum samples was used to stop anyadditional ex vivo deuterium loss prior to analysis. Typically, no morethan 2 deuterium atoms were replaced by hydrogen. For Compound 435(S),there is a deuterium at the methinyl position which was lost uponoxidation to the keto-compound 409. Reduction of 409 to an M1 metaboliteintroduced a proton at the methinyl position. When serum from animalsdosed with 435(S) were analyzed to quantitate administered compound andmetabolites, compound species were included with one and two less sidechain deuteriums in the total amounts (referred to hereinafter as the“−1D” and the “−2D” species). Thus, for Compound 435(S) and Compound 409separate ion pairs were set up to detect the compound and itscorresponding −1D and −2D species. For Compound 435(S) three ion pairswere detected: m/z 291/197, 290/197, and 189/197. For Compound 409 ionpairs of m/z 288/186, 287/186 and 286/186 were monitored. Inclusion of−1D and −2D species in the measurements of Compound 409 and Compound435(S) more accurately quantitates the total active species and isreasonable based on what is known about the metabolism and activities ofpentoxifylline and its M-1 metabolites. Increased plasma exposure toCompound 409 or any M-1 metabolites of 409 would be desirable. Thisincludes the −1D and −2D species.

For the corresponding deuterated M5 metabolite (M5a):

which has no deuterium on its acid side chain, only one ion pair wasused at m/z 271/225. The internal standard for the analysis wasindiplon.

TABLE 12 Pharmacokinetic Results After Oral Administration of 435(S) and(S)-M1 in Rats. Compound(s) Measured^(a) AUC_(0-∞) (hr*ng/mL) C_(max)(ng/mL) 435(S)  4507 ± 1015 4105 ± 964 (S)-M1 1628 ± 272 1570 ± 249 %Difference^(b) +177% +162% 435(S) + 409 13464 ± 3502 15647 ± 7421(S)-M1 + pentoxifylline 4632 ± 437 5032 ± 630 % Difference^(b) +191%+212% Deuterated M5 (M5a) 1924 ± 183 M5 2985 ± 601 % Difference^(b) −36% ^(a)Mass observed via LC-MS/MS. Stereochemistry presumed to be≧95% (S) based on published pentoxifylline metabolism reports. ^(b)%Difference = [(deuterated species) − (nondeuteratedspecies)](100)/(nondeuterated species)

The results of the oral administration in rats are shown in Table 12.The deuterated Compound 435(S) demonstrated a significantly higherAUC_(0-∞) and C_(max) than its undeuterated counterpart (S)-M1. Becausethere is a significant serum interconversion between (S)-M1 andpentoxifylline and both species are therapeutically active, we alsoquantitated AUC_(O-∞) and C_(max) for (S)-M1 together withpentoxifylline, and for Compound 435(S) together with Compound 409.Compound 435(S) together with Compound 409 demonstrated a significantlyhigher AUC_(0-∞) and C_(max) than did (S)-M1 together withpentoxifylline after the oral administration of (S)-M1 and 435(S)respectively.

The AUC_(0-∞) was also measured for the M-5 and M5a metabolites arisingfrom the oral administration of (S)-M1 and 435(S), respectively. The M-5metabolite may be associated with toxicity in certain patients and isconsidered undesirable. Table 12 shows that oral administration ofCompound 435(S) provides considerably less M5a compared to the level ofM5 obtained after administration of non-deuterated (S)-M1. The ratio ofactive species to M5 metabolite was much more favorable for thedeuterated compounds than for the non-deuterated compounds. The ratio of(Compound 435(S)+Compound 409) to M5a was 7.0, which was much betterthan the ratio of 1.6 for ((S)-M1+pentoxifylline) to M5.

TABLE 13 Pharmacokinetic Results After Intravenous Administration inRats. Compound(s) Measured^(a) AUC_(0-∞) (hr*ng/mL) 435(S) 7127 ± 816(S)-M1 3390 ± 302 % Difference^(b) +110%  435(S) + 409 11247 ± 1326(S)-M1 + pentoxifylline 6280 ± 460 % Difference^(b) +79% Deuterated M5(M5a) 1522 ± 530 M5 1795 ± 521 % Difference^(b) −15% ^(a)Mass observedvia LC-MS/MS. Stereochemistry presumed to be ≧95% (S) based on publishedpentoxifylline metabolism reports. ^(b)% Difference = [(deuteratedspecies) − (nondeuterated species)](100)/(nondeuterated species)

Table 13 shows the results following intravenous administration in rats.The results for intravenous administration were similar to those fororal administration. Compound 435(S) had an average AUC_(0-∞) that was110% greater than its undeuterated counterpart (S)-M1 after intravenousadministration. Compound 435(S) together with Compound 409 had anaverage AUC_(O-∞) that was 79% greater than (S)-M1 together withpentoxifylline after intravenous administration. Intravenousadministration of Compound 435(S) provides an amount of M5a metabolitethat is 15% less than the amount of M5 metabolite than is provided byintravenous administration of (S)-M1. The ratio of active species to thecorresponding M5 metabolite in rats that were intravenously administeredCompound 435(S) was 7.4 as compared to 3.5 for rats that wereintravenously administered (S)-M1.

Example 19 Pharmacokinetic Study of Pentoxifylline and Compound 435(S)in Chimps After Oral and Intravenous Dosing

Pentoxifylline and Compound 435(S) were separately dissolved in warm(65° C.) saline at a concentration at 10 mg/mL. A 1:1 mixture of the twocompounds was then prepared containing a final concentration of 5 mg/mLof each compound and the mixture was then sterile filtered through a0.2-μm filter.

Two chimps (one male and one female) were used in each of the oral andintravenous studies. Animals were fasted overnight prior toadministration of compounds. All animals were sedated with ketamine(approximately 10 mg/kg) and/or telazol (approximately 5 mg/kg) prior todosing. Intravenous administration was achieved by IV infusion of 75 mgof each compound (15 mL total dosing solution) over 10 minutes. Oraladministration was achieved by oral gavage of a single 75 mg dose ofeach compound (15 mL total dosing solution). Blood samples (6 mL) werecollected from the dosed chimps at various times prior to and afterdosing. For intravenous administrations blood samples were collected at0 min (preinfusion), 5 min, 9.5 min (immediately before the end of theinfusion), then 6, 15, 30 and 45 min, and 1, 2, 4, 6, 8, 10 and 12 hrafter the infusion is stopped. For oral administrations, blood sampleswere collected at 0 min (predose), 15 and 30 min, and 1, 1.5, 2, 4, 6,8, 10 and 12 hr postdose.

Blood samples were placed in tubes containing sodium heparin, mixed andstored on ice until centrifuged. Within 30 minutes of collection, plasmawas isolated by centrifuging the blood samples and removing an aliquot(200 μL) of the resulting plasma. Each 200-μL aliquot of plasma wasmixed with 400 μL acetonitrile and stored at −70° C. until furtheranalysis by LC-MS/MS using an Applied Bio-systems API 4000 massspectrometer.

The analysis of all samples by LC-MS/MS was performed as described abovefor the rat plasma samples in Example 18.

TABLE 14 Pharmacokinetic Results Following Oral Administration inChimps. AUC_(0-∞) (hr*ng/mL) Compound(s) Measured^(a) Male Female 435(S)829 672 (S)-M1 300 301 % Difference^(b) +176% +123% 435(S) + 409 1097 1277  (S)-M1 + pentoxifylline 414 525 % Difference^(b) +165% +143%Deuterated M5 (M5a) 462 606 M5 1456  1868  % Difference^(b)  −68%  −68%^(a)Mass observed via LC-MS/MS. Stereochemistry presumed to be ≧95% (S)based on published pentoxifylline metabolism reports. ^(b)% Difference =[(deuterated species) − (nondeuterated species)](100)/(nondeuteratedspecies)

Table 14 shows the results of oral administration of 435(S) andpentoxifylline in chimps. Following oral administration of a 1:1combination of Compound 435(S) and pentoxifylline, both Compound 435(S)and its corresponding ketone Compound 409 demonstrated significantlyhigher average AUC_(0-∞) values than the corresponding undeuteratedcounterparts, (S)-M1 and pentoxifylline. The average AUC_(0-∞) forCompound 435(S) together with Compound 409 was significantly higher thanthe average AUC_(0-∞) for (S)-M1 together with pentoxifylline. Inaddition, the average AUC_(0-∞) for the undesired deuterated M-5metabolite (M5a) was significantly lower than that of the undeuteratedM-5. Finally, the ratio of active species to M5 metabolite for thedeuterated compounds {(435(S)+409): (deuterated M5)} was approximately8-fold higher than the corresponding ratio for the undeuterated species{((S)-M1+pentoxifylline): M5}.

TABLE 15 Pharmacokinetic Results Following Intravenous Administration inChimps. AUC_(0-∞) (hr*ng/mL) Compound(s) Measured^(a) Male Female 435(S)2522 1213 (S)-M1 1559  657 % Difference^(b) +61% +84% 435(S) + 409 32191607 (S)-M1 + pentoxifylline 2285 1018 % Difference^(b) +40% +57%Deuterated M5  428  632 M5 1195 1560 % Difference^(b) −65% −60% ^(a)Massobserved via LC-MS/MS. Stereochemistry presumed to be ≧95% (S) based onpublished pentoxifylline metabolism reports. ^(b)% Difference =[(deuterated species) − (nondeuterated species)](100)/(nondeuteratedspecies)

Table 15 shows the results of intravenous administration of 435(S) andpentoxifylline in chimps. The results following intravenousadministration showed favorable differentiation of the deuteratedcompounds, though not as pronounced as those observed following oraladministration. Compared to administration of pentoxifylline, theamounts of active species produced from the administration of Compound435(S) were between 40 and 57% higher, while the amounts of M5metabolite produced decreased by between 60 and 65%. The ratio of activespecies to M5 metabolite in chimps that were intravenously administeredCompound 435(S) was approximately 4-fold higher than in chimpsadministered pentoxifylline.

The above results show that compounds of this invention providesignificantly greater plasma exposure of desired active species than thecorresponding non-deuterated compounds. Moreover, deuterium substitutionin the present compounds was shown to reduce levels of the M5metabolite, which may be associated with intolerability inrenally-impaired patients.

Without further description, it is believed that one of ordinary skillin the art can, using the preceding description and the illustrativeexamples, make and utilize the compounds of the present invention andpractice the claimed methods. It should be understood that the foregoingdiscussion and examples merely present a detailed description of certainpreferred embodiments. It will be apparent to those of ordinary skill inthe art that various modifications and equivalents can be made withoutdeparting from the spirit and scope of the invention.

1-22. (canceled)
 23. A compound of Formula I:

or a pharmaceutically acceptable salt thereof, wherein: each of R¹ andR² is —CH₃; R³ is —CD₃; R⁴ is ^(∀)CD₂(CH₂)₃, wherein “∀” represents theportion of the R⁴ moiety bound to C(Y¹)(Y²) in the compound; Y¹ is OH;and Y² is hydrogen, wherein the isotopic enrichment factor for eachdesignated deuterium atom is at least
 5000. 24. The compound of claim23, wherein any atom not designated as deuterium is present at itsnatural isotopic abundance.
 25. The compound of claim 23, whereinisotopic enrichment factor for each designated deuterium atom is atleast
 6000. 26. The compound of claim 23, wherein isotopic enrichmentfactor for each designated deuterium atom is at least
 6600. 27. Apharmaceutical composition comprising a compound of claim 24 and apharmaceutically acceptable carrier.
 28. A method of treating a diseaseor condition in a patient in need thereof, comprising administering tothe patient an effective amount of a compound of claim 24, wherein thedisease is selected from diabetic nephropathy and hypertensivenephropathy.
 29. A method of treating chronic kidney disease in apatient in need thereof, comprising administering to the patient aneffective amount of a compound of claim
 24. 30. The method of claim 29wherein the chronic kidney disease is glomerulonephritis, focalsegmental glomerulosclerosis, nephrotic syndrome, reflux uropathy, orpolycystic kidney disease.
 31. A method of treating chronic disease ofthe liver in a patient in need thereof, comprising administering to thepatient an effective amount of a compound of claim
 24. 32. The method ofclaim 31 wherein the chronic disease of the liver is nonalcoholicsteatohepatitis, fatty liver degeneration or other diet-induced high fator alcohol-induced tissue-degenerative conditions, cirrhosis, liverfailure, or alcoholic hepatitis.
 33. A method of treating adiabetes-related disease or condition in a patient in need thereof,comprising administering to the patient an effective amount of acompound of claim 24, wherein the disease or condition is selected frominsulin resistance, retinopathy, diabetic ulcers, radiation-associatednecrosis, acute kidney failure or drug-induced nephrotoxicity.
 34. Acompound of Formula A:

or a pharmaceutically acceptable salt thereof, wherein: each of R¹ andR² is independently selected from —CH₃ or —CD₃; R³ is —CD₃; R⁴ is^(∀)CD₂(CH₂)₃, wherein “∀” represents the portion of the R⁴ moiety boundto C(Y¹)(Y²) in the compound; R⁵ is H or D; Y¹ is OH; and Y² ishydrogen, wherein the isotopic enrichment factor for each designateddeuterium atom is at least
 5000. 35. The compound of claim 34, whereinany atom not designated as deuterium is present at its natural isotopicabundance.
 36. The compound of claim 34, wherein isotopic enrichmentfactor for each designated deuterium atom is at least
 6000. 37. Thecompound of claim 34, wherein isotopic enrichment factor for eachdesignated deuterium atom is at least
 6600. 38. A pharmaceuticalcomposition comprising a compound of claim 35 and a pharmaceuticallyacceptable carrier.
 39. A method of treating a disease or condition in apatient in need thereof, comprising administering to the patient aneffective amount of a compound of claim 35 wherein the disease isselected from diabetic nephropathy and hypertensive nephropathy.
 40. Amethod of treating chronic kidney disease in a patient in need thereof,comprising administering to the patient an effective amount of acompound of claim
 35. 41. The method of claim 40 wherein the chronickidney disease is glomerulonephritis, focal segmentalglomerulosclerosis, nephrotic syndrome, reflux uropathy, or polycystickidney disease.
 42. A method of treating chronic disease of the liver ina patient in need thereof, comprising administering to the patient aneffective amount of a compound of claim
 35. 43. The method of claim 42wherein the chronic disease of the liver is nonalcoholicsteatohepatitis, fatty liver degeneration or other diet-induced high fator alcohol-induced tissue-degenerative conditions, cirrhosis, liverfailure, or alcoholic hepatitis.
 44. A method of treating adiabetes-related disease or condition in a patient in need thereof,comprising administering to the patient an effective amount of acompound of claim 35, wherein the disease or condition is selected frominsulin resistance, retinopathy, diabetic ulcers, radiation-associatednecrosis, acute kidney failure or drug-induced nephrotoxicity.
 45. Aracemic mixture comprising i) the compound of claim 23 or apharmaceutically acceptable salt thereof; and ii) the enantiomer of thecompound of claim 23 or a pharmaceutically acceptable salt thereof. 46.A racemic mixture comprising i) the compound of claim 34 or apharmaceutically acceptable salt thereof; and ii) the enantiomer of thecompound of claim 48 or a pharmaceutically acceptable salt thereof.